AMQPClassic Component

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An easy-to-use AMQP 0.9.1 client implementation, with support for RabbitMQ extensions.

Syntax

TiotAMQPClassic

Remarks

The AMQPClassic component provides an easy-to-use AMQP 0.9.1 client implementation, and it also supports certain RabbitMQ extensions to the AMQP 0.9.1 specification. The component supports both plaintext and TLS-enabled connections over TCP.

Connecting

The AMQP 0.9.1 transport protocol has two layers: an overall connection between the client and server, and one or more channels running over that connection.

The component implements both layers, so the first step is to initiate the overall connection. Set the AuthScheme, User, Password, SSLEnabled, and VirtualHost properties if necessary, then call the ConnectTo method, passing it the server's hostname and port number. (If the server in question is not running RabbitMQ, disabling the RabbitMQCompatible configuration setting before connecting is also recommended.)

The next step is to create at least one channel, which can be accomplished by using the CreateChannel method. The component allows creating any number of channels, up to the limit specified by the MaxChannelCount configuration setting.

Connecting and Creating a Channel // The examples in this documentation use a RabbitMQ server, which requires SASL Plain auth. amqpc1.AuthScheme = AmqpclassicAuthSchemes.smSASLPlain; amqpc1.User = "guest"; amqpc1.Password = "guest"; amqpc1.SSLEnabled = true; amqpc1.ConnectTo("amqpclassic.test-server.com", 5671); amqpc1.CreateChannel("channel");

Once the component has connected to the server, and one or more channels have been opened, the component can begin manipulating exchanges and queues, publishing messages, and creating consumers.

Note that most AMQP 0.9.1 operations can themselves vary in their complexity. The examples below are intentionally simple for the sake of clarity and brevity, but links are provided for many other parts of the component's API where more detail can be found.

Declaring Exchanges

The DeclareExchange method is used to declare (i.e., create, or verify the existence of) exchanges on the server. While all AMQP servers provide a default, direct-type exchange that all queues are bound to automatically (using their name as the routing key), more complex use-cases will often require creating additional exchanges of varying types.

Declaring an Exchange // Declare a direct-type exchange. amqpc1.DeclareExchange("channel", "MyExchange", "direct", false, false, false, false);

Exchanges can also be deleted using the DeleteExchange method.

Declaring Queues

The DeclareQueue method is used to declare (i.e., create, or verify the existence of) queues on the server. Unlike with exchanges, the server does not provide any queues by default, so declaring a queue is always necessary (unless one has already been created by another client, or configured ahead-of-time on the server itself).

Declaring a Queue // Declare a queue. amqpc1.DeclareQueue("channel", "MyQueue", false, false, false, false, false);

Queues may also be deleted or purged using the DeleteQueue and PurgeQueue methods.

Binding Queues to Exchanges

The BindQueue method is used to bind a queue to an exchange. Exchanges use the information held by their queue bindings to determine which messages to forward to which queues.

Note that all AMQP 0.9.1 servers automatically bind all queues to their default exchange (which is always a direct exchange with no name) using each queue's name as the binding's routing key. This makes it easy to send a message to a specific queue without having to declare bindings; just call PublishMessage, pass empty string for ExchangeName, and the name of the desired queue for RoutingKey.

Binding a Queue to an Exchange // Bind a queue to an exchange. Messages will only be delivered to the queue if their routing key is "MyRoutingKey". amqpc1.BindQueue("channel", "MyQueue", "MyExchange", "MyRoutingKey", false);

Queues can also be unbound from exchanges using the UnbindQueue method.

Publishing Messages

To publish a message, populate the Message* properties, and then call the PublishMessage method.

Publishing a Message amqpc1.Message.Body = "Hello, world!"; // Publish a message to the server's default (no-name) exchange, using the name of a specific queue as the routing key. amqpc1.PublishMessage("channel", "", "MyQueue", false, false); // Publish a message to the "MyExchange" exchange, using the routing key "MyRoutingKey". amqpc1.PublishMessage("channel", "MyExchange", "MyRoutingKey", false, false);

Note that outgoing messages may be handled differently by the server if the channel they are sent over is in transaction or (for RabbitMQ only) "publish confirmations" mode. Refer to the EnableTransactionMode and EnablePublishConfirms methods for more information.

Receiving Messages

There are two possible ways for the component to receive a message:

• Messages can be asynchronously pushed to the component from the server. At any point in time, the server may push a message to the component from a queue that the Consume method has been used to attach a consumer to.
• Messages can be synchronously pulled from the server by the component. The FetchMessage method is used to attempt to pull (or "fetch") messages from a specific queue.

Regardless of how they are received, all incoming messages cause the ReceivedMessage* properties to be populated and the MessageIn event to fire.

Receiving a Message // MessageIn event handler. amqpc1.OnMessageIn += (s, e) => { if (e.MessageCount == -1) { // The server pushed a message to us asynchronously due to a consumer we created. Console.WriteLine("The server pushed this message to us via consumer '" + e.ConsumerTag + "':"); Console.WriteLine(amqpc1.ReceivedMessage.Body); } else if (e.DeliveryTag > 0) { // We pulled a message from a queue with the FetchMessage() method. Console.WriteLine("Message successfully pulled:"); Console.WriteLine(amqpc1.ReceivedMessage.Body); Console.WriteLine(e.MessageCount + " messages are still available to pull."); } else { // We tried to pull a message, but there were none available to pull. Console.WriteLine("No messages available to pull."); } }; // Attach a consumer to "MyQueue". amqpc1.Consume("channel", "MyQueue", "consumerTag", false, true, false, false); // Or, try to fetch a message from "MyQueue". amqpc1.FetchMessage("channel", "MyQueue", true);

Note that the MessageIn event always fires if FetchMessage is called successfully, even if there were no messages available to fetch; refer to MessageIn for more information.

Property List

The following is the full list of the properties of the component with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the component with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the component with short descriptions. Click on the links for further details.

Arguments Property (AMQPClassic Component)

A collection of table fields that specify arguments to send to the server when calling certain methods.

Syntax

property Arguments: TiotAMQPCTableFieldList read get_Arguments write set_Arguments;

Remarks

This property holds a collection of AMQPCTableField objects representing additional arguments sent when one of the following methods is called:

• Consume
• DeclareExchange
• DeclareQueue
• BindQueue
• UnbindQueue

Arguments are typically server-dependent; refer to your server's documentation to determine what, if any, arguments are supported for each of the above methods.

This property is not available at design time.

AuthScheme Property (AMQPClassic Component)

The authentication scheme to use when connecting.

Syntax

property AuthScheme: TiotTAuthSchemes read get_AuthScheme write set_AuthScheme;

TiotTAuthSchemes = (
  smNone,
  smSASLAnonymous,
  smSASLPlain,
  smSASLExternal
);

Default Value

smSASLPlain

Remarks

This property controls what authentication scheme the component should use when connecting to the remote host.

Valid values are:

• smNone (0)
• smSASLAnonymous (1)
• smSASLPlain (2) - Default
• smSASLExternal (3)

This property is not available at design time.

Channels Property (AMQPClassic Component)

Collection of active channels.

Syntax

property Channels: TiotAMQPCChannelList read get_Channels;

Remarks

This collection property holds a list of AMQPCChannel items, one for each currently active channel.

Refer to CreateChannel and CloseChannel for more information.

This property is read-only and not available at design time.

ClientProperties Property (AMQPClassic Component)

A collection of table fields that describe properties of the client.

Syntax

property ClientProperties: TiotAMQPCTableFieldList read get_ClientProperties write set_ClientProperties;

Remarks

This property holds a collection of AMQPCTableField objects representing client properties. During the connection process, these properties will be sent to the server.

While the component does not send any client properties by default, it is common for AMQP clients to send "product", "version", and "platform" properties to help identify themselves.

This property is not available at design time.

Connected Property (AMQPClassic Component)

This property triggers a connection or disconnection.

Syntax

property Connected: Boolean read get_Connected write set_Connected;

Default Value

false

Remarks

This property triggers a connection or disconnection. Setting this property to True makes the component attempt to connect to the host identified by the RemoteHost property. If successful, after the connection is achieved, the value of the property changes to True and the Connected event is fired.

Setting this property to False closes the connection. How and when the connection is closed is controlled by the Linger property.

Note: It is recommended to use the Connect or Disconnect method instead of setting this property.

This property is not available at design time.

Firewall Property (AMQPClassic Component)

A set of properties related to firewall access.

Syntax

property Firewall: TiotFirewall read get_Firewall write set_Firewall;

Remarks

This is a Firewall-type property, which contains fields describing the firewall through which the component will attempt to connect.

Heartbeat Property (AMQPClassic Component)

The heartbeat timeout value.

Syntax

property Heartbeat: Integer read get_Heartbeat write set_Heartbeat;

Default Value

0

Remarks

This property specifies the heartbeat timeout value, in seconds. Heartbeats are disabled if set to 0 (default).

Before connecting, this property can be set to indicate the desired heartbeat timeout value. During the connection process, the component and the server will compare their desired heartbeat values and choose the lower one.

Once connected, this property will reflect the agreed-upon heartbeat value. While the connection is idle, heartbeats are sent by both the component and the server approximately once every (Heartbeat / 2) seconds. If either side has not received a heartbeat (or other transmission) for ~Heartbeat seconds, it will consider the other side unreachable and close the connection.

This setting cannot be changed while connected.

This property is not available at design time.

IncomingMessages Property (AMQPClassic Component)

Collection of incoming messages which are waiting for acknowledgement.

Syntax

property IncomingMessages: TiotAMQPCMessageList read get_IncomingMessages;

Remarks

This property holds a collection of AMQPCMessage objects that represent incoming messages the component has yet to send acknowledgements to the server for.

Refer to the MessageIn event for more information about message acknowledgements.

This property is read-only and not available at design time.

LocalHost Property (AMQPClassic Component)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

property LocalHost: String read get_LocalHost write set_LocalHost;

Default Value

''

Remarks

The LocalHost property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multi-homed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

LocalPort Property (AMQPClassic Component)

The TCP port in the local host where the component binds.

Syntax

property LocalPort: Integer read get_LocalPort write set_LocalPort;

Default Value

0

Remarks

This property must be set before a connection is attempted. It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting this property to 0 (default) enables the system to choose an open port at random. The chosen port will be returned by the LocalPort property after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set this property when a connection is active will generate an error.

This property is useful when trying to connect to services that require a trusted port in the client side.

Message Property (AMQPClassic Component)

The message to send.

Syntax

property Message: TiotAMQPCMessage read get_Message write set_Message;

Remarks

This property holds an AMQPCMessage object whose fields are used to construct a message to send when PublishMessage is called.

Refer to PublishMessage for more information.

Publishing a Message amqpc1.Message.Body = "Hello, world!"; // Publish a message to the server's default (no-name) exchange, using the name of a specific queue as the routing key. amqpc1.PublishMessage("channel", "", "MyQueue", false, false); // Publish a message to the "MyExchange" exchange, using the routing key "MyRoutingKey". amqpc1.PublishMessage("channel", "MyExchange", "MyRoutingKey", false, false);

This property is not available at design time.

OutgoingMessages Property (AMQPClassic Component)

Collection of outgoing messages which are waiting for acknowledgement.

Syntax

property OutgoingMessages: TiotAMQPCMessageList read get_OutgoingMessages;

Remarks

This property holds a collection of AMQPCMessage objects that represent outgoing messages the component has yet to receive acknowledgements from the server for.

Refer to the PublishMessage method for more information.

This property is read-only and not available at design time.

Password Property (AMQPClassic Component)

A password to use for SASL authentication.

Syntax

property Password: String read get_Password write set_Password;

Default Value

''

Remarks

This property contains a password to use for SASL authentication.

This property is not available at design time.

QueueMessageCount Property (AMQPClassic Component)

The message count returned by various queue operations.

Syntax

property QueueMessageCount: Integer read get_QueueMessageCount;

Default Value

0

Remarks

This property is populated with a message count after calling certain queue-related methods.

This property is read-only and not available at design time.

ReceivedMessage Property (AMQPClassic Component)

The last message received.

Syntax

property ReceivedMessage: TiotAMQPCMessage read get_ReceivedMessage;

Remarks

This property is an AMQPCMessage object which represents the last message received by the component. It is populated by the component automatically each time a message is received.

Refer to Consume, FetchMessage, and MessageIn for more information.

This property is read-only and not available at design time.

RemoteHost Property (AMQPClassic Component)

This property includes the address of the remote host. Domain names are resolved to IP addresses.

Syntax

property RemoteHost: String read get_RemoteHost write set_RemoteHost;

Default Value

''

Remarks

This property specifies the IP address (IP number in dotted internet format) or the domain name of the remote host. It is set before a connection is attempted and cannot be changed once a connection is established.

If this property is set to a domain name, a DNS request is initiated, and upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, an error is returned.

If the component is configured to use a SOCKS firewall, the value assigned to this property may be preceded with an "*". If this is the case, the host name is passed to the firewall unresolved and the firewall performs the DNS resolution.

Example. Connecting:

TCPClientControl.RemoteHost = "MyHostNameOrIP" TCPClientControl.RemotePort = 777 TCPClientControl.Connected = true

RemotePort Property (AMQPClassic Component)

The port of the AQMP server (default is 5672). The default port for SSL is 5671.

Syntax

property RemotePort: Integer read get_RemotePort write set_RemotePort;

Default Value

5672

Remarks

This property specifies a service port on the remote host to connect to.

A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

This property is not available at design time.

ServerProperties Property (AMQPClassic Component)

A collection of table fields that describe properties of the server.

Syntax

property ServerProperties: TiotAMQPCTableFieldList read get_ServerProperties;

Remarks

After connecting, this property will hold a collection of AMQPCTableField objects representing server properties.

This property is read-only and not available at design time.

SSLAcceptServerCertEncoded Property (AMQPClassic Component)

This is the certificate (PEM/base64 encoded).

Syntax

property SSLAcceptServerCertEncoded: String read get_SSLAcceptServerCertEncoded write set_SSLAcceptServerCertEncoded;
property SSLAcceptServerCertEncodedB: TBytes read get_SSLAcceptServerCertEncodedB write set_SSLAcceptServerCertEncodedB;

Default Value

''

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The Store and Subject properties also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

This property is not available at design time.

SSLCertEncoded Property (AMQPClassic Component)

This is the certificate (PEM/base64 encoded).

Syntax

property SSLCertEncoded: String read get_SSLCertEncoded write set_SSLCertEncoded;
property SSLCertEncodedB: TBytes read get_SSLCertEncodedB write set_SSLCertEncodedB;

Default Value

''

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The Store and Subject properties also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

This property is not available at design time.

SSLCertStore Property (AMQPClassic Component)

This is the name of the certificate store for the client certificate.

Syntax

property SSLCertStore: String read get_SSLCertStore write set_SSLCertStore;
property SSLCertStoreB: TBytes read get_SSLCertStoreB write set_SSLCertStoreB;

Default Value

'MY'

Remarks

This is the name of the certificate store for the client certificate.

The StoreType property denotes the type of the certificate store specified by Store. If the store is password protected, specify the password in StorePassword.

Store is used in conjunction with the Subject property to specify client certificates. If Store has a value, and Subject or Encoded is set, a search for a certificate is initiated. Please see the Subject property for details.

Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

When the certificate store type is PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

SSLCertStorePassword Property (AMQPClassic Component)

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

Syntax

property SSLCertStorePassword: String read get_SSLCertStorePassword write set_SSLCertStorePassword;

Default Value

''

Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

SSLCertStoreType Property (AMQPClassic Component)

This is the type of certificate store for this certificate.

Syntax

property SSLCertStoreType: TiotCertStoreTypes read get_SSLCertStoreType write set_SSLCertStoreType;

TiotCertStoreTypes = (
  cstUser,
  cstMachine,
  cstPFXFile,
  cstPFXBlob,
  cstJKSFile,
  cstJKSBlob,
  cstPEMKeyFile,
  cstPEMKeyBlob,
  cstPublicKeyFile,
  cstPublicKeyBlob,
  cstSSHPublicKeyBlob,
  cstP7BFile,
  cstP7BBlob,
  cstSSHPublicKeyFile,
  cstPPKFile,
  cstPPKBlob,
  cstXMLFile,
  cstXMLBlob,
  cstJWKFile,
  cstJWKBlob,
  cstSecurityKey,
  cstBCFKSFile,
  cstBCFKSBlob,
  cstPKCS11,
  cstAuto
);

Default Value

cstUser

Remarks

This is the type of certificate store for this certificate.

The component supports both public and private keys in a variety of formats. When the cstAuto value is used, the component will automatically determine the type. This property can take one of the following values:

SSLCertSubject Property (AMQPClassic Component)

This is the subject of the certificate used for client authentication.

Syntax

property SSLCertSubject: String read get_SSLCertSubject write set_SSLCertSubject;

Default Value

''

Remarks

This is the subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=support@nsoftware.com". Common fields and their meanings are as follows:

If a field value contains a comma, it must be quoted.

SSLEnabled Property (AMQPClassic Component)

Whether TLS/SSL is enabled.

Syntax

property SSLEnabled: Boolean read get_SSLEnabled write set_SSLEnabled;

Default Value

false

Remarks

This setting specifies whether TLS/SSL is enabled in the component. When False (default) the component operates in plaintext mode. When True TLS/SSL is enabled.

TLS/SSL may also be enabled by setting SSLStartMode. Setting SSLStartMode will automatically update this property value.

If the default port (5672) is selected when SSLEnabled is set to true, the port will automatically be changed to the default port for AMQP with SSL (5671). Likewise, if port 5671 is selected when SSLEnabled is set to false, the port will automatically be changed to the default port. If the port has been set to any value other than the default values, it will remain the same when the value of SSLEnabled changes.

This property is not available at design time.

SSLProvider Property (AMQPClassic Component)

This specifies the SSL/TLS implementation to use.

Syntax

property SSLProvider: TiotTSSLProviders read get_SSLProvider write set_SSLProvider;

TiotTSSLProviders = (
  sslpAutomatic,
  sslpPlatform,
  sslpInternal
);

Default Value

sslpAutomatic

Remarks

This property specifies the SSL/TLS implementation to use. In most cases the default value of 0 (Automatic) is recommended and should not be changed. When set to 0 (Automatic) the component will select whether to use the platform implementation or the internal implementation depending on the operating system as well as the TLS version being used.

Possible values are:

In most cases using the default value (Automatic) is recommended. The component will select a provider depending on the current platform.

When Automatic is selected, on Windows the component will use the platform implementation. On Linux/macOS the component will use the internal implementation. When TLS 1.3 is enabled via SSLEnabledProtocols the internal implementation is used on all platforms.

SSLServerCertEncoded Property (AMQPClassic Component)

This is the certificate (PEM/base64 encoded).

Syntax

property SSLServerCertEncoded: String read get_SSLServerCertEncoded;
property SSLServerCertEncodedB: TBytes read get_SSLServerCertEncodedB;

Default Value

''

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The Store and Subject properties also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

This property is read-only and not available at design time.

Timeout Property (AMQPClassic Component)

A timeout for the component.

Syntax

property Timeout: Integer read get_Timeout write set_Timeout;

Default Value

60

Remarks

If the Timeout property is set to 0, all operations return immediately, potentially failing with a WOULDBLOCK error if data cannot be sent immediately.

If Timeout is set to a positive value, data is sent in a blocking manner and the component will wait for the operation to complete before returning control. The component will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of Timeout seconds.

The component will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the operation is not yet complete, the component raises an exception.

Please note that by default, all timeouts are inactivity timeouts, i.e. the timeout period is extended by Timeout seconds when any amount of data is successfully sent or received.

The default value for the Timeout property is 60 seconds.

User Property (AMQPClassic Component)

A username to use for SASL authentication.

Syntax

property User: String read get_User write set_User;

Default Value

''

Remarks

This property contains a username to use for SASL authentication.

This property is not available at design time.

VirtualHost Property (AMQPClassic Component)

The virtual host to connect to.

Syntax

property VirtualHost: String read get_VirtualHost write set_VirtualHost;

Default Value

'/'

Remarks

This property specifies the virtual host to connect to on the server, and is set to / by default.

Note that the configuration of the server defines what virtual hosts are available.

This setting cannot be changed while connected.

This property is not available at design time.

BindQueue Method (AMQPClassic Component)

Binds a queue to an exchange.

Syntax

procedure BindQueue(ChannelName: String; QueueName: String; ExchangeName: String; RoutingKey: String; NoWait: Boolean);

Remarks

This method is used to bind the queue named QueueName to the exchange named ExchangeName. Exchanges use bindings to determine which queues to route messages to.

Multiple bindings between the same queue and exchange with different RoutingKeys and/or arguments are allowed; requests that would create a duplicate binding are ignored. No queue will ever receive duplicate copies of any message, regardless of what bindings are present on the server.

Note that all AMQP 0.9.1 servers automatically bind all queues to their default exchange (which is always a direct exchange with no name) using each queue's name as the binding's routing key. This makes it easy to send a message to a specific queue without having to declare bindings; just call PublishMessage, pass empty string for ExchangeName, and the name of the desired queue for RoutingKey.

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

QueueName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

The server's default exchange may be specified by passing empty string for ExchangeName. Otherwise, ExchangeName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

The RoutingKey parameter specifies the binding's routing key. Exchanges that use routing-key-based logic make some sort of comparison between the routing keys of incoming messages and this value to decide which messages should be forwarded to the specified queue. Examples of exchange types which use routing keys include:

• direct exchanges, which compare (for equality) the routing keys of incoming messages to the routing keys of each queue bound to them.
• topic exchanges, which match the routing keys of incoming messages against the routing pattern of each queue bound to them.

Not all exchange types make use of routing keys, in which case empty string can be passed for the RoutingKey parameter. Examples of exchange types which don't use routing keys include:

• fanout exchanges simply forward incoming messages to all queues bound to them, unconditionally.
• header exchanges only forward messages that include certain headers. When binding a queue to a header exchange, add items to the Argument* properties to describe the headers that eligible messages must have, and whether they must have any or all of those headers.

Note that the format of the RoutingKey parameter and/or the content of the Argument* properties may differ slightly between server implementations. Refer to your server's documentation to determine what it expects to receive for each exchange type that it supports.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• No queue with the given QueueName exists.
• No exchange with the given ExchangeName exists.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Binding a Queue to an Exchange // Bind a queue to an exchange. Messages will only be delivered to the queue if their routing key is "MyRoutingKey". amqpc1.BindQueue("channel", "MyQueue", "MyExchange", "MyRoutingKey", false);

CancelConsume Method (AMQPClassic Component)

Cancels an existing consumer.

Syntax

procedure CancelConsume(ChannelName: String; ConsumerTag: String; NoWait: Boolean);

Remarks

This method requests that the server cancel the consumer identified by the given ConsumerTag on the channel specified by ChannelName.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because no consumer with the given ConsumerTag exists.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

CloseChannel Method (AMQPClassic Component)

Closes a channel.

Syntax

procedure CloseChannel(ChannelName: String);

Remarks

This method closes the channel named ChannelName and removes it from the Channel* properties.

If no channel with the given ChannelName exists, an exception will be thrown.

CommitTransaction Method (AMQPClassic Component)

Commits the current transaction for a channel.

Syntax

procedure CommitTransaction(ChannelName: String);

Remarks

This method commits the current transaction for the channel with the given ChannelName. A new transaction is started immediately after the current one is committed.

Refer to EnableTransactionMode for more information about transactions.

An exception is thrown if a channel with the given ChannelName doesn't exist, or if the server returns an error because the channel does not have transaction mode enabled.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Config Method (AMQPClassic Component)

Sets or retrieves a configuration setting.

Syntax

function Config(ConfigurationString: String): String;

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Connect Method (AMQPClassic Component)

This method connects to a remote host.

Syntax

procedure Connect();

Remarks

This method connects to the remote host specified by RemoteHost and RemotePort. For instance: component.RemoteHost = "MyHostNameOrIP"; component.RemotePort = 7777; component.Connect();

ConnectTo Method (AMQPClassic Component)

This method connects to a remote host.

Syntax

procedure ConnectTo(Host: String; Port: Integer);

Remarks

This method connects to the remote host specified by the Host and Port parameters. For instance: component.ConnectTo("MyHostNameOrIP", 777)

Consume Method (AMQPClassic Component)

Starts a new consumer for a given queue.

Syntax

procedure Consume(ChannelName: String; QueueName: String; ConsumerTag: String; NoLocal: Boolean; NoAck: Boolean; Exclusive: Boolean; NoWait: Boolean);

Remarks

This method instructs the server to start a new consumer on the queue named QueueName; once the consumer is created, it will cause messages enqueued to the specified queue to be delivered to the component over the channel specified by ChannelName.

Consumers last as long as the channel they were created on, or until they are cancelled using the CancelConsume method. Each time a message is delivered to the component, it is immediately added to the IncomingMessage* properties, the ReceivedMessage* properties are populated, and the MessageIn event fires.

ConsumerTag is a string which uniquely identifies the new consumer on the specified channel. If empty string is passed for ConsumerTag, the server will generate a consumer tag automatically when it creates the . this auto-generated consumer tag can then be retrieved by querying the ConsumerTag configuration setting after this method returns.

The NoLocal parameter, if True, ensures that the consumer never consumes messages published on the same channel. (Note that this functionality is not available on RabbitMQ servers, which ignore the NoLocal parameter).

The NoAck parameter controls whether the server will expect the component to acknowledge the each message delivered. Refer to MessageIn for more information about acknowledging messages.

The Exclusive parameter, if True, will cause the component to request that the server create an exclusive consumer. Attaching an exclusive consumer to a queue prevents any other consumers from consuming messages from that queue.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

Additional arguments may be sent with this request by adding them to the Argument* properties. Arguments are server-dependent; refer to your server's documentation to determine if any additional arguments apply for this request.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• No queue with the given QueueName exists.
• The given ConsumerTag is already in use on the specified channel.
• An exclusive consumer was requested for a queue which already has consumers attached to it.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Receiving a Message // MessageIn event handler. amqpc1.OnMessageIn += (s, e) => { if (e.MessageCount == -1) { // The server pushed a message to us asynchronously due to a consumer we created. Console.WriteLine("The server pushed this message to us via consumer '" + e.ConsumerTag + "':"); Console.WriteLine(amqpc1.ReceivedMessage.Body); } else if (e.DeliveryTag > 0) { // We pulled a message from a queue with the FetchMessage() method. Console.WriteLine("Message successfully pulled:"); Console.WriteLine(amqpc1.ReceivedMessage.Body); Console.WriteLine(e.MessageCount + " messages are still available to pull."); } else { // We tried to pull a message, but there were none available to pull. Console.WriteLine("No messages available to pull."); } }; // Attach a consumer to "MyQueue". amqpc1.Consume("channel", "MyQueue", "consumerTag", false, true, false, false); // Or, try to fetch a message from "MyQueue". amqpc1.FetchMessage("channel", "MyQueue", true);

CreateChannel Method (AMQPClassic Component)

Creates a new channel.

Syntax

procedure CreateChannel(ChannelName: String);

Remarks

This method creates a new channel with the name ChannelName and adds it to the Channel* properties. If a channel with the given ChannelName already exists, an error will be thrown.

Connecting and Creating a Channel // The examples in this documentation use a RabbitMQ server, which requires SASL Plain auth. amqpc1.AuthScheme = AmqpclassicAuthSchemes.smSASLPlain; amqpc1.User = "guest"; amqpc1.Password = "guest"; amqpc1.SSLEnabled = true; amqpc1.ConnectTo("amqpclassic.test-server.com", 5671); amqpc1.CreateChannel("channel");

DeclareExchange Method (AMQPClassic Component)

Verifies that an exchange exists, potentially creating it if necessary.

Syntax

procedure DeclareExchange(ChannelName: String; ExchangeName: String; ExchangeType: String; Passive: Boolean; Durable: Boolean; AutoDelete: Boolean; NoWait: Boolean);

Remarks

This method is used to verify that an exchange named ExchangeName exists; and potentially creates it if no such exchange exists.

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

ExchangeName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters, and must not begin with amq. unless the Passive parameter is True.

ExchangeType specifies the exchange type. All servers support the direct and fanout exchange types, and most should also support the topic and header exchange types. Some servers may support additional, custom exchange types as well. Refer to your server's documentation for more information about each exchange type, and to determine what exchange types it supports other than direct and fanout.

If Passive is True, the server will only verify that an exchange with the given ExchangeName actually exists (regardless of how it is configured).

If Passive is False, and no exchange named ExchangeName currently exists, the server will create one.

If Passive is False, and there is a preexisting exchange named ExchangeName, the server will verify that its current configuration matches the given parameters and arguments.

Durable specifies what happens to the exchange in the event of a server restart. Durable exchanges will be recreated, while non-durable (transient) exchanges will not.

AutoDelete specifies whether the server should automatically delete the exchange when all queues have been unbound from it. Note that this parameter is only sent if the RabbitMQCompatible configuration setting is enabled; it is ignored otherwise.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

Additional arguments may be sent with this request by adding them to the Argument* properties. Arguments are server-dependent; refer to your server's documentation to determine if any additional arguments apply for this request.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• One of the parameter constraints described above was violated.
• One of the verification cases described above fails.
• The value passed for ExchangeType did not correspond to an exchange type supported by the server.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Declaring an Exchange // Declare a direct-type exchange. amqpc1.DeclareExchange("channel", "MyExchange", "direct", false, false, false, false);

DeclareQueue Method (AMQPClassic Component)

Verifies that a queue exists, potentially creating it if necessary.

Syntax

procedure DeclareQueue(ChannelName: String; QueueName: String; Passive: Boolean; Durable: Boolean; Exclusive: Boolean; AutoDelete: Boolean; NoWait: Boolean);

Remarks

This method is used to verify that a queue named QueueName exists; and potentially creates it if no such queue exists.

After each successful call to this method, the component populates the QueueMessageCount property, as well as the QueueConsumerCount and QueueName configuration settings. Refer to each one for more information.

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

If creating a new queue, empty string can be passed for QueueName to have the server automatically generate a name for the new queue (which can then be retrieved using the QueueName configuration setting). In all other cases, QueueName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters, and must not begin with amq. unless the Passive parameter is True.

If Passive is True, the server will only verify that a queue with the given QueueName actually exists (regardless of how it is configured).

If Passive is False, and no queue named QueueName currently exists, the server will create one.

If Passive is False, and there is a preexisting queue named QueueName, the server will verify that its current configuration matches the given parameters and arguments.

Durable specifies what happens to the queue in the event of a server restart. Durable queue will be recreated, while non-durable (transient) queue will not. (Note that the messages in durable queues will still be lost unless they are marked as persistent.)

Exclusive, if True, indicates that the queue may only be accessed by the current connection. Exclusive queues are deleted when the current connection closes.

AutoDelete specifies whether the server should automatically delete the queue when all consumers have finished using it. (Note that auto-delete queues aren't eligible for deletion until after a consumer attaches to them for the first time.)

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

Additional arguments may be sent with this request by adding them to the Argument* properties. Arguments are server-dependent; refer to your server's documentation to determine if any additional arguments apply for this request.

An exception is thrown if no channel with the given ChannelName exists, if QueueName empty string and NoWait is True, or if the server returns an error because:

• One of the parameter constraints described above was violated.
• One of the verification cases described above fails.
• An attempt was made to verify (i.e., the Passive parameter was True) another connection's exclusive queue.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Declaring a Queue // Declare a queue. amqpc1.DeclareQueue("channel", "MyQueue", false, false, false, false, false);

DeleteExchange Method (AMQPClassic Component)

Deletes an exchange.

Syntax

procedure DeleteExchange(ChannelName: String; ExchangeName: String; IfUnused: Boolean; NoWait: Boolean);

Remarks

This method is used to delete an exchange.

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

ExchangeName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters, and must not begin with amq..

When IfUnused is True, the server will only delete the exchange if no queues are bound to it.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• The value passed for ExchangeName fails one or more of the constraints described above.
• No exchange named ExchangeName exists. (This does not apply for RabbitMQ; attempting to delete a non-existent exchange will always succeed.)
• The IfUnused parameter was True, but the exchange still had one or more queues bound to it.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

DeleteQueue Method (AMQPClassic Component)

Deletes a queue.

Syntax

procedure DeleteQueue(ChannelName: String; QueueName: String; IfUnused: Boolean; IfEmpty: Boolean; NoWait: Boolean);

Remarks

This method is used to delete the queue named QueueName.

After each successful call to this method, the component populates the QueueMessageCount property with the number of messages deleted along with the queue. (Note that this does not occur if the NoWait parameter is set to True.)

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

QueueName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters, and must not begin with amq..

When IfUnused is True, the server will only delete the queue if no consumers are attached to it.

When IfEmpty is True, the server will only delete the queue if it has no messages in it. (When IfEmpty is False, servers will typically move any remaining messages to a dead-letter queue, if one is available.)

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• The value passed for QueueName fails one or more of the constraints described above.
• No queue named QueueName exists. (This does not apply for RabbitMQ; attempting to delete a non-existent queue will always succeed.)
• The IfUnused parameter was True, but the queue still had one or more consumers attached to it.
• The IfEmpty parameter was True, but the queue still had one or more messages in it.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Disconnect Method (AMQPClassic Component)

This method disconnects from the remote host.

Syntax

procedure Disconnect();

Remarks

This method disconnects from the remote host. Calling this method is equivalent to setting the Connected property to False.

DoEvents Method (AMQPClassic Component)

Processes events from the internal message queue.

Syntax

procedure DoEvents();

Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

EnablePublishConfirms Method (AMQPClassic Component)

Enables publish confirmations mode for a channel.

Syntax

procedure EnablePublishConfirms(ChannelName: String; NoWait: Boolean);

Remarks

This method enables publish confirmations mode for the channel with the given ChannelName.

While a channel is in publish confirmations mode, the server will acknowledge each message published by the component. The component will wait to fire the MessageOut event until it receives this acknowledgement. (Note that this mode is only available when the RabbitMQCompatible configuration setting is enabled.)

Note that a channel will stay in publish confirmations mode, once enabled, until it is deleted.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

An exception is thrown if the RabbitMQCompatible configuration setting is currently False, if no channel with the given ChannelName exists, or if EnableTransactionMode has been called for the specified channel previously.

EnableTransactionMode Method (AMQPClassic Component)

Enables transaction mode for a channel.

Syntax

procedure EnableTransactionMode(ChannelName: String);

Remarks

This method enables transaction mode for the channel with the given ChannelName.

While a channel is in transaction mode, all messages published and acknowledgements sent over it will be part of a transaction, and the server will wait to process them until the transaction is either committed or rolled back.

To commit the current transaction on a channel, call CommitTransaction; and to roll it back (and discard the messages and acknowledgements that were part of it), call RollbackTransaction.

Keep in mind that, according to the AMQP 0.9.1 specification:

• A new transaction is always started immediately after committing or rolling back the current one, which means that...
• ...a channel will stay in transaction mode, once enabled, until it is deleted.
• Transactions are only guaranteed to be atomic if all messages published and acknowledgements sent affect a single queue.
• Any messages published on a channel in transaction mode that have the Mandatory or Immediate flags set are not guaranteed to be included in the transaction.

An exception is thrown if no channel with the given ChannelName exists, or if EnablePublishConfirms has been called for the specified channel previously.

FetchMessage Method (AMQPClassic Component)

Attempts to fetch a message from a given queue.

Syntax

procedure FetchMessage(ChannelName: String; QueueName: String; NoAck: Boolean);

Remarks

This method attempts to fetch a message from the queue named QueueName over the channel named ChannelName.

If a message is fetched as a result of this method being called, it is immediately added to the IncomingMessage* properties, the ReceivedMessage* properties are populated, and the MessageIn event fires.

Even if no message gets fetched, the MessageIn event will still fire as long as the request was successful. The server returns the number of available messages in the specified queue in response to all successful fetch requests, and that count is exposed by MessageIn event's MessageCount parameter. Refer to the MessageIn event for more information.

QueueName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

The NoAck parameter controls whether the server will expect the component to acknowledge the fetched message. Refer to MessageIn for more information about acknowledging messages.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• No queue with the given QueueName exists.
• The specified queue exists, but is locked or otherwise unavailable to consume from (e.g., an exclusive consumer might be attached to it).

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Receiving a Message // MessageIn event handler. amqpc1.OnMessageIn += (s, e) => { if (e.MessageCount == -1) { // The server pushed a message to us asynchronously due to a consumer we created. Console.WriteLine("The server pushed this message to us via consumer '" + e.ConsumerTag + "':"); Console.WriteLine(amqpc1.ReceivedMessage.Body); } else if (e.DeliveryTag > 0) { // We pulled a message from a queue with the FetchMessage() method. Console.WriteLine("Message successfully pulled:"); Console.WriteLine(amqpc1.ReceivedMessage.Body); Console.WriteLine(e.MessageCount + " messages are still available to pull."); } else { // We tried to pull a message, but there were none available to pull. Console.WriteLine("No messages available to pull."); } }; // Attach a consumer to "MyQueue". amqpc1.Consume("channel", "MyQueue", "consumerTag", false, true, false, false); // Or, try to fetch a message from "MyQueue". amqpc1.FetchMessage("channel", "MyQueue", true);

Interrupt Method (AMQPClassic Component)

Interrupt the current action and disconnects from the remote host.

Syntax

procedure Interrupt();

Remarks

This method will interrupt the current method (if applicable) and cause the component to disconnect from the remote host.

PublishMessage Method (AMQPClassic Component)

Publishes a message.

Syntax

procedure PublishMessage(ChannelName: String; ExchangeName: String; RoutingKey: String; Mandatory: Boolean; Immediate: Boolean);

Remarks

This method is used to publish the message specified by the Message* properties to the exchange named ExchangeName over the channel specified by ChannelName.

When this method is called, the message to publish is immediately added to the OutgoingMessage* properties, and the MessageOut event fires once it has been sent (or, if the specified channel is in "publish confirmations" mode, after the server has acknowledged it).

Note that all AMQP 0.9.1 servers automatically bind all queues to their default exchange (which is always a direct exchange with no name) using each queue's name as the binding's routing key. This makes it easy to send a message to a specific queue without having to declare bindings; just call PublishMessage, pass empty string for ExchangeName, and the name of the desired queue for RoutingKey.

Note that messages published over channels which are in either transaction or "publish confirmations" mode may be handled differently than they would be on a channel in normal mode. Refer to the EnableTransactionMode and EnablePublishConfirms methods for more information about what each mode entails.

The server's default exchange may be specified by passing empty string for ExchangeName. Otherwise, ExchangeName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

The RoutingKey parameter specifies the message's routing key. Whether this parameter needs to be non-empty, and what format it should have if so, depends on the type of exchange it is being sent to. Some exchange types may use information included with the message, such as its Headers. Refer to BindQueue for more information about how routing keys are used, and to your server's documentation for information on what it expects.

The Mandatory parameter controls what the server should do if the message can't be routed to any queue (either because it isn't eligible for any of the queues bound to the specified exchange because of how their bindings are configured, or because no queues are bound to the exchange in the first place). If True, the server will return the message, at which point the MessageReturned event will be fired. If False, the server will drop the message.

The Immediate parameter controls what the server should do if the message can't be immediately delivered to any consumer (either because it cannot be routed to a queue, or because the queues it can be routed to have no active consumers attached to them). If True, the server will return the message, at which point the MessageReturned event will be fired. If False, the server will queue the message if possible, or drop it if not.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• The value passed for ExchangeName fails one or more of the constraints described above.
• No exchange named ExchangeName exists.
• The message is rejected for some reason.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Publishing a Message amqpc1.Message.Body = "Hello, world!"; // Publish a message to the server's default (no-name) exchange, using the name of a specific queue as the routing key. amqpc1.PublishMessage("channel", "", "MyQueue", false, false); // Publish a message to the "MyExchange" exchange, using the routing key "MyRoutingKey". amqpc1.PublishMessage("channel", "MyExchange", "MyRoutingKey", false, false);

PurgeQueue Method (AMQPClassic Component)

Purges all messages from a queue.

Syntax

procedure PurgeQueue(ChannelName: String; QueueName: String; NoWait: Boolean);

Remarks

This method purges all messages from the queue named QueueName. Messages which have been sent but are awaiting acknowledgement are not affected.

After each successful call to this method, the component populates the QueueMessageCount property with the number of messages purged from the queue. (Note that this does not occur if the NoWait parameter is set to True.)

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

QueueName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

The NoWait parameter, if True, will cause the server to execute the request asynchronously. For asynchronous request handling, the server only sends back a response in case of an error.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because no queue named QueueName exists.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Recover Method (AMQPClassic Component)

Request that the server redeliver all messages on a given channel that have not been acknowledged.

Syntax

procedure Recover(ChannelName: String; Requeue: Boolean);

Remarks

This method is used to request that the server redeliver all messages that it previously sent to the component on the channel specified by ChannelName which are still awaiting acknowledgement.

A call to this method may cause the server to redeliver zero or more messages over the channel specified by ChannelName. Those messages will cause the MessageIn event to fire with its Redelivered event parameter set to True.

The Requeue parameter controls how the server should attempt to redeliver the messages awaiting acknowledgement. If set to True, the server will simple put the messages back on their original queues, and they will be delivered like any other queued messages (potentially to other consumers). If set to False, the server will redeliver the messages to the component directly.

An exception is thrown if no channel with the given ChannelName exists, or (for RabbitMQ only) if the server returns an error because Requeue was False. (RabbitMQ only supports setting Requeue to True.)

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

Reset Method (AMQPClassic Component)

Reset the component.

Syntax

procedure Reset();

Remarks

This method will reset the component's properties to their default values.

ResetMessage Method (AMQPClassic Component)

Resets the Message properties.

Syntax

procedure ResetMessage();

Remarks

This method resets the Message* properties.

RollbackTransaction Method (AMQPClassic Component)

Rolls back the current transaction for a channel.

Syntax

procedure RollbackTransaction(ChannelName: String);

Remarks

This method rolls back the current transaction for the channel with the given ChannelName. A new transaction is started immediately after the current one is rolled back.

Refer to EnableTransactionMode for more information about transactions.

An exception is thrown if a channel with the given ChannelName doesn't exist, or if the server returns an error because the channel does not have transaction mode enabled.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

SetChannelAccept Method (AMQPClassic Component)

Disables or enables message acceptance for a given channel.

Syntax

procedure SetChannelAccept(ChannelName: String; Accept: Boolean);

Remarks

This method is used to disable and enable message acceptance for the channel specified by ChannelName.

A channel is always configured to accept messages when first created, allowing the server to freely deliver messages to the component for any consumers that have been created on that channel using the Consume method.

Disabling message acceptance for a channel prevents the server from automatically delivering messages to the component over it; however, it is still possible to use the FetchMessage method to synchronously attempt to retrieve a message on a channel with message acceptance disabled.

An exception is thrown if no channel with the given ChannelName exists, or (for RabbitMQ only) if the server returns an error because Accept was False. (RabbitMQ does not support disabling message acceptance.)

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

SetQoS Method (AMQPClassic Component)

Requests a specific quality of service (QoS).

Syntax

procedure SetQoS(ChannelName: String; PrefetchSize: Integer; PrefetchCount: Integer; Global: Boolean);

Remarks

This method is used to request a specific quality of service for a certain scope. When the PrefetchSize and/or PrefetchCount are set for a certain scope, the server will limit how many messages it sends to the component before stopping to wait for or or more of them to be acknowledged.

ChannelName is the name of the channel which is used to send the request. Depending on the server and what Global is set to, it may also be significant to the request itself (refer to the Global parameter's description, below, for more information).

PrefetchSize specifies a window size in bytes; i.e., the server will stop sending messages if the total size of all of the currently unacknowledged messages already sent, plus the size of the next message that could be sent, exceeds PrefetchSize bytes. A PrefetchSize of 0 indicates no limit. (Note that RabbitMQ does not support prefetch size limits.)

PrefetchCount specifies the number of unacknowledged messages the server will limit itself to sending. A PrefetchCount of 0 indicates no limit.

Global specifies the scope which the QoS request should apply to. It is interpreted differently based on whether the server is RabbitMQ or not. Refer to this table:

Keep the following things in mind when using QoS:

• The limits specified by a QoS request only affect messages that require acknowledgement.
• How the server chooses to handle interactions between QoS settings at different scopes is server-dependent.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error for any reason.

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

UnbindQueue Method (AMQPClassic Component)

Removes a previously-created queue binding.

Syntax

procedure UnbindQueue(ChannelName: String; QueueName: String; ExchangeName: String; RoutingKey: String);

Remarks

This method removes a previously-created queue binding.

ChannelName controls what channel the component will send the request over. While any channel can technically be used, keep in mind that the server will close it if a channel error occurs. For this reason, it is good practice to make requests such as this one using a channel that is not involved in message publishing or consumption.

QueueName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

The server's default exchange may be specified by passing empty string for ExchangeName. Otherwise, ExchangeName must be a non-empty string consisting only of letters, digits, hyphens, underscores, periods, and colons. It must be no longer than 255 characters.

RoutingKey should be the same routing key used when originally creating the binding that is to be removed. For bindings created using arguments instead of a routing key, the Argument* properties must contain the same items used originally instead.

An exception is thrown if no channel with the given ChannelName exists, or if the server returns an error because:

• No queue with the given QueueName exists. (Does not apply to RabbitMQ.)
• No exchange with the given ExchangeName exists. (Does not apply to RabbitMQ.)

Note that in AMQP, server errors are grouped into "connection errors" and "channel errors", and both are fatal. That is, if the server returns a channel error, it will then close the channel which caused the error; and if it returns a connection error, it will then close the connection. The AMQPClassic component's Error Codes page includes AMQP's various connection and channel errors.

ChannelReadyToSend Event (AMQPClassic Component)

Fires when a channel is ready to send messages.

Syntax

type TChannelReadyToSendEvent = procedure (
  Sender: TObject;
  const ChannelName: String
) of Object;

property OnChannelReadyToSend: TChannelReadyToSendEvent read FOnChannelReadyToSend write FOnChannelReadyToSend;

Remarks

This event fires when a channel is ready to send messages.

ChannelName is the name of the channel.

Connected Event (AMQPClassic Component)

This event is fired immediately after a connection completes (or fails).

Syntax

type TConnectedEvent = procedure (
  Sender: TObject;
  StatusCode: Integer;
  const Description: String
) of Object;

property OnConnected: TConnectedEvent read FOnConnected write FOnConnected;

Remarks

If the connection is made normally, StatusCode is 0 and Description is 'OK'.

If the connection fails, StatusCode has the error code returned by the Transmission Control Protocol (TCP)/IP stack. Description contains a description of this code. The value of StatusCode is equal to the value of the error.

Please refer to the Error Codes section for more information.

ConnectionStatus Event (AMQPClassic Component)

This event is fired to indicate changes in the connection state.

Syntax

type TConnectionStatusEvent = procedure (
  Sender: TObject;
  const ConnectionEvent: String;
  StatusCode: Integer;
  const Description: String
) of Object;

property OnConnectionStatus: TConnectionStatusEvent read FOnConnectionStatus write FOnConnectionStatus;

Remarks

The ConnectionStatus event is fired when the connection state changes: for example, completion of a firewall or proxy connection or completion of a security handshake.

The ConnectionEvent parameter indicates the type of connection event. Values may include the following:

Disconnected Event (AMQPClassic Component)

This event is fired when a connection is closed.

Syntax

type TDisconnectedEvent = procedure (
  Sender: TObject;
  StatusCode: Integer;
  const Description: String
) of Object;

property OnDisconnected: TDisconnectedEvent read FOnDisconnected write FOnDisconnected;

Remarks

If the connection is broken normally, StatusCode is 0 and Description is 'OK'.

If the connection is broken for any other reason, StatusCode has the error code returned by the Transmission Control Protocol (TCP/IP) subsystem. Description contains a description of this code. The value of StatusCode is equal to the value of the TCP/IP error.

Please refer to the Error Codes section for more information.

Error Event (AMQPClassic Component)

Information about errors during data delivery.

Syntax

type TErrorEvent = procedure (
  Sender: TObject;
  ErrorCode: Integer;
  const Description: String
) of Object;

property OnError: TErrorEvent read FOnError write FOnError;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component raises an exception.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Log Event (AMQPClassic Component)

Fires once for each log message.

Syntax

type TLogEvent = procedure (
  Sender: TObject;
  LogLevel: Integer;
  const Message: String;
  const LogType: String
) of Object;

property OnLog: TLogEvent read FOnLog write FOnLog;

Remarks

This event fires once for each log message generated by the component. The verbosity is controlled by the LogLevel setting.

LogLevel indicates the level of the Message. Possible values are:

LogType identifies the type of log entry. Possible values are:

• Info: General information about the component.
• Frame: Frame status messages.

MessageIn Event (AMQPClassic Component)

Fires when a message is received; as well as when an attempt is made to fetch a message from a currently empty queue.

Syntax

type TMessageInEvent = procedure (
  Sender: TObject;
  const ChannelName: String;
  const ConsumerTag: String;
  DeliveryTag: Int64;
  Redelivered: Boolean;
  const ExchangeName: String;
  const RoutingKey: String;
  MessageCount: Integer;
  var Accept: Integer
) of Object;

property OnMessageIn: TMessageInEvent read FOnMessageIn write FOnMessageIn;

Remarks

This event fires anytime a message is received. There are two possible ways for the component to receive a message:

• Messages can be asynchronously pushed to the component from the server. At any point in time, the server may push a message to the component from a queue that the Consume method has been used to attach a consumer to.
• Messages can be synchronously pulled from the server by the component. The FetchMessage method is used to attempt to pull (or "fetch") messages from a specific queue.

This event also fires anytime FetchMessage is called against a queue that currently has no messages available to pull. This is a special case, and results in only the ChannelName and MessageCount event parameters being populated.

Other than that special case, and any exceptions noted below, this event's parameters are populated the same way regardless of the manner in which messages are received.

ChannelName always reflects the name of the associated channel.

ConsumerTag reflects the consumer tag associated with the consumer that caused the server to push the message to the component. (ConsumerTag is always empty for messages pulled from the server by FetchMessage since no consumers are involved.)

DeliveryTag reflects the server-assigned, channel-specific delivery tag number for the incoming message.

Redelivered reflects whether the server is redelivering a message that is has delivered previously.

ExchangeName reflects the name of the exchange to which the incoming message was originally published. (If the message was originally published to the server's default exchange, whose name is always the empty string, ExchangeName will also be empty.)

RoutingKey reflects the routing key that the message was originally published with.

MessageCount is always -1 when this event fires due to a message being pushed to the component by the server. When this event fires as a result of FetchMessage being called, MessageCount reflects the number of messages still available in the queue the component tried to pull a message from (even if there were no messages available to pull).

The Accept parameter can be set to control how the component responds to the incoming message, if it needs to be acknowledged (if the message doesn't need to be acknowledged, the value set to the Accept parameter is ignored). Valid values are:

• 0 - default: Accept the message; send a positive acknowledgement.
• 1: Silently accept the message; don't send any acknowledgement.
• 2: Accept the message; send a cumulative positive acknowledgement coving this, and all previously unacknowledged, messages.
• 3: Reject the message; send a negative acknowledgement for it, and instruct the server not to return it to the queue.
• 4: Reject the message; send a negative acknowledgement for it, and instruct the server to return it to the queue.

If the value provided for the Accept parameter isn't one of those described above, the default (0) will be used instead.

Receiving a Message // MessageIn event handler. amqpc1.OnMessageIn += (s, e) => { if (e.MessageCount == -1) { // The server pushed a message to us asynchronously due to a consumer we created. Console.WriteLine("The server pushed this message to us via consumer '" + e.ConsumerTag + "':"); Console.WriteLine(amqpc1.ReceivedMessage.Body); } else if (e.DeliveryTag > 0) { // We pulled a message from a queue with the FetchMessage() method. Console.WriteLine("Message successfully pulled:"); Console.WriteLine(amqpc1.ReceivedMessage.Body); Console.WriteLine(e.MessageCount + " messages are still available to pull."); } else { // We tried to pull a message, but there were none available to pull. Console.WriteLine("No messages available to pull."); } }; // Attach a consumer to "MyQueue". amqpc1.Consume("channel", "MyQueue", "consumerTag", false, true, false, false); // Or, try to fetch a message from "MyQueue". amqpc1.FetchMessage("channel", "MyQueue", true);

MessageOut Event (AMQPClassic Component)

Fires when a message is published.

Syntax

type TMessageOutEvent = procedure (
  Sender: TObject;
  const ChannelName: String;
  const ExchangeName: String;
  const RoutingKey: String;
  const MessageId: String;
  DeliveryTag: Int64;
  Accepted: Boolean
) of Object;

property OnMessageOut: TMessageOutEvent read FOnMessageOut write FOnMessageOut;

Remarks

This event fires anytime a message is published; or after an outgoing message has been acknowledged by the server, if the channel it was published on is in "publish confirmations" mode.

ChannelName reflects the name of the channel the message was published on.

ExchangeName reflects the name of the exchange the message was published to. (If the message was published to the server's default exchange, whose name is always the empty string, ExchangeName will also be empty.)

RoutingKey reflects the routing key that the message was published with.

MessageId reflects the message's unique Id, if one was set.

DeliveryTag reflects the channel-specific delivery tag number for the message. (Note that this is only populated for messages published on a channel in "publish confirmations" mode; otherwise it will be set to -1.)

Accepted indicates whether the server published back a positive True or negative False acknowledgement for the outgoing message. Note that this is only valid for messages published on a channel in "publish confirmations" mode; Accepted will always be True messages published on a channel in normal or transaction mode.

Refer to EnablePublishConfirms for more information about channels in "publish confirmations" mode.

MessageReturned Event (AMQPClassic Component)

Fires if a previously published message is returned by the server due to it being undeliverable.

Syntax

type TMessageReturnedEvent = procedure (
  Sender: TObject;
  const ChannelName: String;
  ReplyCode: Integer;
  const ReplyText: String;
  const ExchangeName: String;
  const RoutingKey: String
) of Object;

property OnMessageReturned: TMessageReturnedEvent read FOnMessageReturned write FOnMessageReturned;

Remarks

This event fires if the server returns a previously published message because it could not deliver it. Typically, messages are only undeliverable in one of the following situations:

• The message was originally published with the Mandatory option enabled, but there were no queues it could be routed to.
• The message was originally published with the Immediate option enabled, but there were no consumers it could be delivered to immediately on any queue it was routed to (or there were no queues it could be routed to).

The ReceivedMessage* properties will be populated with the returned message.

ChannelName reflects the name of the channel the message was originally published on.

ReplyCode will be an AMQP error code that indicates the reason why the message was returned. (Tip: The AMQPClassic component's Error Codes page includes the various AMQP error codes.)

ReplyText will be a message with further details about why the message was returned.

ExchangeName reflects the name of the exchange to which the message was originally published. (If the message was originally published to the server's default exchange, whose name is always the empty string, ExchangeName will also be empty.)

RoutingKey reflects the routing key that the message was originally published with.

SSLServerAuthentication Event (AMQPClassic Component)

Fired after the server presents its certificate to the client.

Syntax

type TSSLServerAuthenticationEvent = procedure (
  Sender: TObject;
  CertEncoded: String;
  CertEncodedB: TBytes;
  const CertSubject: String;
  const CertIssuer: String;
  const Status: String;
  var Accept: Boolean
) of Object;

property OnSSLServerAuthentication: TSSLServerAuthenticationEvent read FOnSSLServerAuthentication write FOnSSLServerAuthentication;

Remarks

During this event, the client can decide whether or not to continue with the connection process. The Accept parameter is a recommendation on whether to continue or close the connection. This is just a suggestion: application software must use its own logic to determine whether or not to continue.

When Accept is False, Status shows why the verification failed (otherwise, Status contains the string OK). If it is decided to continue, you can override and accept the certificate by setting the Accept parameter to True.

SSLStatus Event (AMQPClassic Component)

Shows the progress of the secure connection.

Syntax

type TSSLStatusEvent = procedure (
  Sender: TObject;
  const Message: String
) of Object;

property OnSSLStatus: TSSLStatusEvent read FOnSSLStatus write FOnSSLStatus;

Remarks

The event is fired for informational and logging purposes only. This event tracks the progress of the connection.

AMQPCChannel Type

Represents an AMQP 0.9.1 channel.

Remarks

This type represents an AMQP 0.9.1 channel.

Fields

Constructors

constructor Create();

AMQPCMessage Type

Represents an AMQP 0.9.1 message.

Remarks

This type represents an AMQP 0.9.1 message.

Fields

[
  { "name": "Header1", "type": "long", "value": 12345678901234 },
  { "name": "Header2", "type": "boolean", "value": "false" },
  { "name": "Header3", "type": "string", "value": "This is a test." }
]

[
  { "type": "int", "value": 23 },
  { "type": "int", "value": -52 },
  { "type": "int", "value": 153325 }
]

Constructors

constructor Create();

AMQPCTableField Type

Represents an AMQP 0.9.1 table field.

Remarks

This type represents an AMQP 0.9.1 table field.

Fields

[
  { "type": "int", "value": 23 },
  { "type": "int", "value": -52 },
  { "type": "int", "value": 153325 }
]

{
  { "name": "Test1", "type": "long", "value": 12345678901234 },
  { "name": "Test2", "type": "boolean", "value": "false" },
  { "name": "Test3", "type": "string", "value": "This is a test." }
}

Constructors

constructor Create();

Firewall Type

This is the firewall the component will connect through.

Remarks

When connecting through a firewall, this type is used to specify different properties of the firewall, such as the firewall Host and the FirewallType.

Fields

Constructors

constructor Create();

Config Settings (AMQPClassic Component)

AMQPClassic Config Settings

TCPClient Config Settings

SSL Config Settings

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

Socket Config Settings

Base Config Settings

Trappable Errors (AMQPClassic Component)

AMQPClassic Errors

TCPClient Errors

SSL Errors

TCP/IP Errors