AMQP Component

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An easy-to-use AMQP 1.0 client implementation.

Syntax

TiotAMQP

Remarks

The AMQP component provides an easy-to-use AMQP 1.0 client implementation. The component supports both plaintext and TLS-enabled connections over TCP.

Connecting

The component implements all three layers of the AMQP 1.0 transport protocol, so the first step is to initiate the overall connection. Set the ContainerId property and call the ConnectTo method, passing it the server's hostname and port number.

Once connected, the next step is to create at least one session, which can be accomplished by using the CreateSession method. The component allows creating any number of sessions, up to the limit specified by the MaxSessionCount configuration setting.

Connecting and Creating a Session amqp1.ContainerId = "testClient"; amqp1.ConnectTo("amqp.test-server.com", 5672); amqp1.CreateSession("TestSession");

After creating a session, the next step is to create one or more links (which are created in the context of a session) so that messages can be sent and/or received. Links are unidirectional, so each one has a sender on one end and a receiver on the other.

The component can function both as a sender node (by opening sender links) and as a receiver node (by opening receiver links). But keep in mind that, since the component is implemented as an AMQP 1.0 client, it must be the one to open links (said another way, the component cannot accept any link requests made by other peers).

As with sessions, the component allows creating any number of links for each session, up to the limit specified by the MaxLinkCountPerSession configuration setting.

Creating Sender Links

The LinkReadyToSend event will fire when the newly created sender link is ready to send messages.

Creating a Sender Link amqp1.OnLinkReadyToSend += (s, e) => { Console.WriteLine("Link '" + e.LinkName + "' is ready to send messages!"); }; amqp1.CreateSenderLink("TestSession", "TestSenderLink", "TestTarget");

Sending Messages

At minimum, the Value and ValueType properties must be set. All other properties are optional, though specifying a unique value for MessageId is recommended. (If the GenerateMessageId configuration setting is enabled, the component will generate one automatically when the message is sent.)

Once the Message property's properties have be assigned as desired, call the SendMessage method, passing it the name of an existing sender link on which the message should be sent.

The MessageOut event will be fired when the message has been sent (and acknowledged, if Settled was set to false). The MessageOutcome event may also fire, if necessary, once the receiver reports the outcome of the message.

Refer to SendMessage, MessageOut, and MessageOutcome for more information.

Sending a Message amqp1.OnMessageOut += (s, e) => { Console.WriteLine("Message with Id '" + e.MessageId + "' has been sent on link '" + e.LinkName + "'."); }; amqp1.Message.MessageId = "TestMessageId"; amqp1.Message.Value = "Hello, world!"; amqp1.Message.ValueType = AMQPValueTypes.mvtString; amqp1.SendMessage("TestSenderLink");

The ResetMessage method can be used to reset the Message property's properties to their default values.

Sending Composite AMQP Data

The component supports sending composite AMQP data in a message through the use of JSON with a well-defined schema. Refer to the SendMessage method's documentation for more information and examples.

Creating Receiver Links

The ReceiveMode property controls which receive mode newly-created receiver links will use; refer to its documentation for more information.

After ensuring that ReceiveMode is set as desired, call CreateReceiverLink, passing it the name of an existing session, a unique name for the link, and (if necessary in your environment) the name of a source for the sender to route the link creation request to.

Creating a Receiver Link // Creating an automatic receiver link. amqp1.ReceiveMode = AmqpReceiveModes.rmAutomatic; amqp1.CreateReceiverLink("TestSession", "TestAutoReceiverLink", "TestSource1"); // Creating a retrieve-based receiver link. amqp1.ReceiveMode = AmqpReceiveModes.rmRetrieve; amqp1.CreateReceiverLink("TestSession", "TestRetrieveReceiverLink", "TestSource2");

Receiving Messages

For receiver links created in retrieve-based mode, the component will attempt to "retrieve" a message each time the RetrieveMessage method is called (optionally timing out after a time, if RetrieveTimeout is non-zero). When calling RetrieveMessage, pass it the name of a retrieve-based receiver link.

Regardless of whether a messages is received automatically or retrieved, any incoming message will cause the component to fire the MessageIn event and update the ReceivedMessage property's properties.

When the MessageIn event fires, its State event parameter can be used to specify the outcome of the message, which the component will then transmit back to the sender (as well as self-report by firing the MessageOutcome event). Refer to MessageIn for more information.

Receiving a Message // For automatic receiver links, only the event handler is necessary. amqp1.OnMessageIn += (s, e) => { Console.WriteLine("Message with Id '" + e.MessageId + "' has been received on link '" + e.LinkName + "'. Value:"); Console.WriteLine(amqp1.ReceivedMessage.Value); // The message state is already set to the "Accepted" outcome by default, but we'll set it again // for the purpose of this example. e.State = 0; // 0 = Accepted. }; // For retrieve-based links, it's also necessary to call RetrieveMessage(). It is recommended that the // RetrieveTimeout property be set to a non-zero value (60 seconds is the default) so that the retrieve // request will eventually time out if the sender doesn't have any messages available to deliver. amqp1.RetrieveTimeout = 60; amqp1.RetrieveMessage("TestRetrieveReceiverLink");

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.

AuthScheme Property (AMQP 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.

Connected Property (AMQP Component)

This property indicates whether the component is connected.

Syntax

property Connected: Boolean read get_Connected;

Default Value

false

Remarks

This property indicates whether the component is connected to the remote host. Use the Connect and Disconnect methods to manage the connection.

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

ContainerId Property (AMQP Component)

The container Id the component should advertise when connecting.

Syntax

property ContainerId: String read get_ContainerId write set_ContainerId;

Default Value

''

Remarks

This property specifies the container Id that the component should advertise when it's connecting to the remote host.

In AMQP, the top-level organizational grouping is called a "container", and each container can contain zero or more "nodes", which are the actual entities which send and receive messages over links.

Since this component handles multiple layers of the AMQP transport protocol (the overall connection, the sessions in that connection, and the links attached to those sessions), it must be given a unique container Id.

Note: The container Id cannot be changed while connected.

This property is not available at design time.

Firewall Property (AMQP 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.

IdleTimeout Property (AMQP Component)

The maximum period of inactivity the component will allow before disconnecting.

Syntax

property IdleTimeout: Integer read get_IdleTimeout write set_IdleTimeout;

Default Value

0

Remarks

This property controls how long, in seconds, the component will allow the connection to sit idle before it disconnects from the remote host.

This property may be set to 0 to prevent the component from ever closing the connection due to inactivity.

Note: The idle timeout cannot be changed while connected.

This property is not available at design time.

IncomingMessages Property (AMQP Component)

Collection of incoming messages which have not been fully settled.

Syntax

property IncomingMessages: TiotAMQPMessageList read get_IncomingMessages;

Remarks

This collection property holds a list of AMQPMessage items, one for each incoming message that has not been fully settled by the component (and, potentially, the remote host).

Refer to ReceiveMode for more information.

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

Links Property (AMQP Component)

Collection of active links.

Syntax

property Links: TiotAMQPLinkList read get_Links;

Remarks

This collection property holds a list of AMQPLink items, one for each currently active link.

Refer to CreateReceiverLink, CreateSenderLink, and CloseLink for more information.

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

LocalHost Property (AMQP 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

This 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 multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the component initiate connections (or accept in the case of server components) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

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 multihomed 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 (AMQP 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 on the client side.

Message Property (AMQP Component)

The message to send.

Syntax

property Message: TiotAMQPMessage read get_Message write set_Message;

Remarks

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

Refer to SendMessage for more information. amqp.Message.ValueType = AMQPValueTypes.mvtString; amqp.Message.Value = "Hello World!"; amqp.SendMessage("SenderLinkName");

This property is not available at design time.

OutgoingMessages Property (AMQP Component)

Collection of outgoing messages which have not been fully settled.

Syntax

property OutgoingMessages: TiotAMQPMessageList read get_OutgoingMessages;

Remarks

This collection property holds a list of AMQPMessage items, one for each outgoing message that has not been fully settled by the component (and, potentially, the remote host).

Refer to SendMessage for more information.

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

Password Property (AMQP 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.

ReadyToSend Property (AMQP Component)

Indicates whether the component is ready to send data.

Syntax

property ReadyToSend: Boolean read get_ReadyToSend;

Default Value

false

Remarks

This property indicates that the underlying TCP/IP subsystem is ready to accept data. This is True after connecting to the remote host, and will become False if a call to SendMessage fails due to a WOULDBLOCK condition.

Once data can be sent again, the ReadyToSend event will fire and this property will be True.

If a WOULDBLOCK error occurs while sending a message the component will automatically complete the transmission when sending is possible. No action needs to be taken to re-send the message. ReadyToSend will fire after the component completes any partially sent messages.

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

ReceivedMessage Property (AMQP Component)

The last message received.

Syntax

property ReceivedMessage: TiotAMQPMessage read get_ReceivedMessage;

Remarks

This property is an AMQPMessage object which represents the last message received by the component. It is set by the component automatically each time the MessageIn event fires.

Refer to MessageIn for more information.

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

ReceiveMode Property (AMQP Component)

Controls what mode new receiver links are created with.

Syntax

property ReceiveMode: TiotAMQPReceiveModes read get_ReceiveMode write set_ReceiveMode;

TiotAMQPReceiveModes = (
  rmAutomatic,
  rmRetrieve
);

Default Value

rmAutomatic

Remarks

This property controls which receive mode newly created receiver links should use to receive messages from the sender. Valid values are:

• rmAutomatic (0 - default)
• rmRetrieve (1)

Receiving Messages Automatically

In this mode, receiver links will be created with the amount of credit, and the credit threshold, specified by the DefaultCredit and DefaultCreditThreshold configuration settings. Anytime the link's credit reaches the credit threshold, the component will automatically set it back to its initial value.

Retrieving Messages On-Demand

In this mode, receiver links will be created with no credit (regardless of what DefaultCredit is set to). When RetrieveMessage is called, the component will supply the sender with a single credit and then block until a message is received (if the RetrieveTimeout property is set to zero).

If RetrieveTimeout is non-zero, the component will only block for the specified number of seconds; once that time expires, it will instruct the sender to consume the credit. If the sender chooses to consume the credit by incrementing the value of the LinkDeliveryCount property rather than by sending a message, then the component will throw an error indicating a timeout.

Refer to RetrieveMessage and RetrieveTimeout for more information. amqp.ReceiveMode = AmqpReceiveModes.rmRetrieve; amqp.CreateReceiverLink("SessionID", "ReceiverLinkName", "SomeTarget");

This property is not available at design time.

RemoteHost Property (AMQP 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 (AMQP 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.

RetrieveTimeout Property (AMQP Component)

How long the component should wait for a message to be received after RetrieveMessage is called.

Syntax

property RetrieveTimeout: Integer read get_RetrieveTimeout write set_RetrieveTimeout;

Default Value

60

Remarks

This property controls how long, in seconds, the component will wait for a message to be received after RetrieveMessage is called before timing out the request. If set to zero, the component will wait indefinitely.

Refer to RetrieveMessage for more information.

This property is not available at design time.

Sessions Property (AMQP Component)

Collection of active sessions.

Syntax

property Sessions: TiotAMQPSessionList read get_Sessions;

Remarks

This collection property holds a list of AMQPSession items, one for each currently active session.

Refer to CreateSession and CloseSession for more information.

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

SSLAcceptServerCert Property (AMQP Component)

Instructs the component to unconditionally accept the server certificate that matches the supplied certificate.

Syntax

property SSLAcceptServerCert: TiotCertificate read get_SSLAcceptServerCert write set_SSLAcceptServerCert;

Remarks

If it finds any issues with the certificate presented by the server, the component will normally terminate the connection with an error.

You may override this behavior by supplying a value for SSLAcceptServerCert. If the certificate supplied in SSLAcceptServerCert is the same as the certificate presented by the server, then the server certificate is accepted unconditionally, and the connection will continue normally.

Note: This functionality is provided only for cases in which you otherwise know that you are communicating with the right server. If used improperly, this property may create a security breach. Use it at your own risk.

SSLCert Property (AMQP Component)

The certificate to be used during Secure Sockets Layer (SSL) negotiation.

Syntax

property SSLCert: TiotCertificate read get_SSLCert write set_SSLCert;

Remarks

This property includes the digital certificate that the component will use during SSL negotiation. Set this property to a valid certificate before starting SSL negotiation. To set a certificate, you may set the Encoded field to the encoded certificate. To select a certificate, use the store and subject fields.

SSLEnabled Property (AMQP Component)

This property indicates whether Transport Layer Security/Secure Sockets Layer (TLS/SSL) is enabled.

Syntax

property SSLEnabled: Boolean read get_SSLEnabled write set_SSLEnabled;

Default Value

false

Remarks

This property 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 (AMQP Component)

The Secure Sockets Layer/Transport Layer Security (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 as follows:

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.

SSLServerCert Property (AMQP Component)

The server certificate for the last established connection.

Syntax

property SSLServerCert: TiotCertificate read get_SSLServerCert;

Remarks

This property contains the server certificate for the last established connection.

SSLServerCert is reset every time a new connection is attempted.

This property is read-only.

Timeout Property (AMQP Component)

This property includes the 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.

Note: By default, all timeouts are inactivity timeouts, that is, 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 (AMQP 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.

CloseLink Method (AMQP Component)

Closes a link.

Syntax

procedure CloseLink(Name: String);

Remarks

This method closes the link named Name and removes it from the Links properties. If no link with the given Name exists, an error will be thrown.

CloseSession Method (AMQP Component)

Closes a session.

Syntax

procedure CloseSession(Name: String);

Remarks

This method closes the session named Name and removes it from the Sessions properties. If no session with the given Name exists, an error will be thrown.

Any links open on the specified session when this method is called will be automatically closed and removed from the Links properties.

Config Method (AMQP 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 (AMQP 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 (AMQP 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)

CreateReceiverLink Method (AMQP Component)

Creates a new receiver link with the given name on the specified session.

Syntax

procedure CreateReceiverLink(SessionName: String; Name: String; Source: String);

Remarks

This method creates a new receiver link with the given Name on the session specified by SessionName and adds it to the Links properties. If a link (sender or receiver) with the given Name already exists, or if no session with the given SessionName exists, an error will be thrown.

Source may be set to specify the address of the node at the remote host which should act as the sender. This may not be necessary in all environments, in which case an empty string will suffice.

Receiver links can operate in one of two receive modes: automatic, where the component will work to ensure that messages are received as soon as they are available; and retrieve-based, where the component will only "retrieve" a new message when explicitly instructed to.

The ReceiveMode property controls which receive mode newly-created receiver links will use; refer to its documentation for more information.

AMQP 1.0's transport protocol has three layers: an overarching connection between two containers, the sessions opened on that connection, and the links (between the containers' nodes) attached to those sessions. amqp.ReceiveMode = AmqpReceiveModes.rmRetrieve; amqp.CreateReceiverLink("SessionID", "ReceiverLinkName", "SomeTarget");

CreateSenderLink Method (AMQP Component)

Creates a new sender link with the given name on the specified session.

Syntax

procedure CreateSenderLink(SessionName: String; Name: String; Target: String);

Remarks

This method creates a new sender link with the given Name on the session specified by SessionName and adds it to the Links properties. If a link (sender or receiver) with the given Name already exists, or if no session with the given SessionName exists, an error will be thrown.

Target may be set to specify the address of the node at the remote host which should act as the receiver. This may not be necessary in all environments, in which case an empty string will suffice.

The LinkReadyToSend event will fire when a newly-created sender link is ready to send.

Sender links are created using the Mixed settle mode by default, letting the value of the Settled property control whether each message is settled (the default) or unsettled when it is sent. The DefaultSenderSettleMode configuration setting can be used to control the settle mode that new sender links are created with. Refer to SendMessage for more information on message settlement in general.

AMQP 1.0's transport protocol has three layers: an overarching connection between two containers, the sessions opened on that connection, and the links (between the containers' nodes) attached to those sessions.

CreateSession Method (AMQP Component)

Creates a new session with the given name.

Syntax

procedure CreateSession(Name: String);

Remarks

This method creates a new session with the given Name and adds it to the Sessions properties. If a session with the given Name already exists, an error will be thrown.

AMQP 1.0's transport protocol has three layers: an overarching connection between two containers, the sessions opened on that connection, and the links (between the containers' nodes) attached to those sessions.

Disconnect Method (AMQP 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 (AMQP Component)

This method 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.

Interrupt Method (AMQP Component)

This method interrupts the current action.

Syntax

procedure Interrupt();

Remarks

This method interrupts the current action. If you use SendFile to upload a file, the component will run synchronously until the upload is completed. This method will allow you to stop the file from uploading without disconnecting from the host.

Reset Method (AMQP Component)

This method will reset the component.

Syntax

procedure Reset();

Remarks

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

ResetMessage Method (AMQP Component)

Resets the Message properties.

Syntax

procedure ResetMessage();

Remarks

This method resets the Message property.

RetrieveMessage Method (AMQP Component)

Retrieves a single message over the specified receiver link.

Syntax

procedure RetrieveMessage(LinkName: String);

Remarks

When RetrieveMessage is called, the component will supply the sender with a single credit and then block until a message is received (if the RetrieveTimeout property is set to zero).

If RetrieveTimeout is non-zero, the component will only block for the specified number of seconds; once that time expires, it will instruct the sender to consume the credit. If the sender chooses to consume the credit by incrementing the value of the LinkDeliveryCount property rather than by sending a message, then the component will throw an error indicating a timeout.

LinkName specifies the receiver link which should retrieve a message; if there is no such link, if the specified link is not a receiver link, or if the specified receiver link is not operating in rmSyncGet (1) mode, an error is thrown.

Refer to ReceiveMode and RetrieveTimeout for more information.

SendMessage Method (AMQP Component)

Sends a message on the specified link.

Syntax

procedure SendMessage(LinkName: String);

Remarks

This method sends a message on the link specified by LinkName.

The Message property holds an AMQPMessage object whose properties are used to construct the message to send. At minimum, specify a Value and a ValueType. amqp.Message.ValueType = AMQPValueTypes.mvtString; amqp.Message.Value = "Hello World!"; amqp.SendMessage("SenderLinkName");

Message Settlement

• Settled - All messages will be sent in a settled state.
• Unsettled - All messages will be sent in an unsettled state.
• Mixed - Messages may be sent either settled or unsettled.

• First - Incoming messages will be settled immediately (and the sender will be notified that the message has been received, if the message was not already settled when sent).
• Second - Incoming messages will be settled after the sender has settled them (and the sender will be notified when a message has been received, if the message was not already settled when sent).

Together, the sender's and receiver's settle modes can form the following delivery guarantees:

It is important to note that the message settlement system has a big caveat: Whichever party opens the link can only request that the other end use a specific settle mode. For example, if the component opens a sender link, it has control over the sender settle mode it will use, but it can only request that the remote host use a specific receiver settle mode; so if the component requests that the receiver use Second, the receiver can instead choose to use First (if, e.g., it doesn't support Second).

The component currently only ever requests (and itself only supports) the First receiver settle mode since no other AMQP implementations appear to support the Second receiver settle mode at this time.

The component requests (and uses) the Mixed sender settle mode by default, but supports all of the sender settle modes (the default can be changed using the DefaultSenderSettleMode configuration setting). Sender links created with the Mixed sender use the value of the Settled property to determine whether to send messages as settled or unsettled.

Sending Composite Data

Composite Data JSON Schema

The component uses JSON with a well-defined schema to represent composite data. The composite data JSON schema consists almost entirely of "type-value" objects, which hold an AMQP typename and a value. The syntax for a type-value object is:

{
  "type": "typename",
  "value": value
}

The following table provides a complete list of valid typenames, and describes how the associated values should be represented:

Arrays, Lists, and Maps

The AMQP data model defines three data structure types: array, list, and map. In the composite data JSON schema, their value is always a JSON array that contains zero or more type-value objects. Data structure types may be nested arbitrarily to any depth.

Note that the array and map data structures each have restrictions on their content:

• The elements in an array must all be of the same type (e.g., their typenames must match).
• The elements in a map represent keys (odd-numbered elements) and values (even-numbered elements). There must be an even number of elements (or none), and the values of the "key" elements must be unique.

{
  "type": "map",
  "value": [
    { "type": "symbol", "value": "key1" },
    { "type": "string", "value": "value1" },
    { "type": "symbol", "value": "key2" },
    { "type": "int", "value": 100 }
  ]
}

Described Types

As noted above, AMQP's data model includes the idea of "described types", which is simply a normal AMQP type annotated by a descriptor. The descriptor defines what the data it is associated with represents as a whole.

In the composite data JSON schema, a described type object is just a normal type-value object with an extra "descriptor" property on it (and the "descriptor" property's value is itself a normal type-value object). The syntax for a described type object is:

{
  "descriptor": { "type": "typename", "value": value },
  "type": "typename",
  "value": value
}

Described type objects can be used anywhere that normal type-value objects can be, except as the value of the "descriptor" property for another described type object, which must be a normal type-value object.

Note that, according to the AMQP specification, the type of the descriptor itself ulong or symbol, but the component does not enforce this.

Abbreviated Value Syntax

For brevity, it is possible to abbreviate both normal type-value objects and described type objects when their value type is null, boolean, or string.

For normal type-value objects, instead of using the standard syntax (e.g., { "type": "string", "value": "Hello, world!" }), just use the raw value itself (e.g., "Hello, world!"). Keep in mind that the abbreviated value must still be valid JSON; notably, strings must still be surrounded by quotes (e.g., "value", not value).

The abbreviated syntax for a described type object is a bit different; the "descriptor" property still needs to be associated with the value using a JSON object. To abbreviate a described type object, just exclude the "type" property, like so:

{
  "descriptor": { "type": "typename", "value": value },
  "value": value
}

The abbreviated value syntax can be used anywhere that an unabbreviated type-value object or described type object would normally be used.

The component defaults to using the abbreviated syntax when returning composite data JSON. This can be configured using the SimplifiedJSONFormat configuration setting.

Composite Data JSON Example

{
  "descriptor": { "type": "symbol", "value": "nsoftware:compositeDataExample" },
  "type": "list",
  "value": [
    "Shorthand string value",
    null,
    true,
    { "type": "uuid", "value": "12345678-0000-1000-8000-00805F9B34FB" },
    {
      "type": "array",
      "value": [
        { "type": "uint", "value": 23 },
        { "type": "uint", "value": 52 },
        { "type": "uint", "value": 153325 }
      ]
    },
    {
      "type": "map",
      "value": [
        { "type": "symbol", "value": "name" },
        "Freezer temperature",
        { "type": "symbol", "value": "unit" },
        "Fahrenheit",
        { "type": "symbol", "value": "value" },
        { "type": "int", "value": -2 }
      ]
    },
    {
      "descriptor": { "type": "symbol", "value": "nsoftware:utf8Bytes" },
      "type": "binary",
      "value": "48656C6C6F2C20776F726C6421"
    }
  ]
}

Connected Event (AMQP Component)

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 (AMQP Component)

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

This 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 (AMQP Component)

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 (AMQP Component)

Fired when information is available 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.

LinkReadyToSend Event (AMQP Component)

Fires when a sender link is ready to send messages.

Syntax

type TLinkReadyToSendEvent = procedure (
  Sender: TObject;
  const LinkName: String;
  LinkIndex: Integer
) of Object;

property OnLinkReadyToSend: TLinkReadyToSendEvent read FOnLinkReadyToSend write FOnLinkReadyToSend;

Remarks

This event fires when a sender link is ready to send messages.

LinkName is the name of the sender link.

LinkIndex is the index of the sender link in the Links properties.

Log Event (AMQP 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.
• Session: Session status messages.
• Frame: Frame status messages.

MessageIn Event (AMQP Component)

Fires when the component receives a message.

Syntax

type TMessageInEvent = procedure (
  Sender: TObject;
  const SessionName: String;
  SessionIndex: Integer;
  const LinkName: String;
  LinkIndex: Integer;
  const MessageId: String;
  var State: Integer
) of Object;

property OnMessageIn: TMessageInEvent read FOnMessageIn write FOnMessageIn;

Remarks

This event fires whenever the component receives a message. The message itself is automatically stored in the ReceivedMessage property.

Specifying a Delivery Outcome

• 0: Accepted - The message has been processed successfully.
• 1: Rejected - The message failed to process successfully. Includes an error describing why.
• 2: Released - The message has not been (and will not be) processed.
• 3: Modified - Same as "Released", but with additional metadata for the sender.

When State is set to Rejected (1), the component will include error metadata when it informs the sender of the outcome. Set the RejectErrorCondition and RejectErrorDescription configuration settings before the event handler finishes to specify this error information.

When State is set to Modified (3), the component can include additional metadata when it informs the sender of the outcome. Set zero or more of the ModifiedDeliveryFailed, ModifiedMessageAnnotations, and ModifiedUndeliverableHere configuration settings before the event handler finishes to specify this additional metadata.

Other Parameters

SessionIndex is the index of the session in the Sessions collection property.

LinkName is the name of the link the message was transmitted on.

LinkIndex is the index of the link in the Links collection property.

MessageId is the Id of the message; it may be empty if a message Id was not set.

MessageOut Event (AMQP Component)

Fires when the component sends a message.

Syntax

type TMessageOutEvent = procedure (
  Sender: TObject;
  const SessionName: String;
  SessionIndex: Integer;
  const LinkName: String;
  LinkIndex: Integer;
  const MessageId: String
) of Object;

property OnMessageOut: TMessageOutEvent read FOnMessageOut write FOnMessageOut;

Remarks

This event fires whenever the component sends a message.

SessionName is the name of the session the message was transmitted on.

SessionIndex is the index of the session in the Sessions collection property.

LinkName is the name of the link the message was transmitted on.

LinkIndex is the index of the link in the Links collection property.

MessageId is the Id of the message; it may be empty if a message Id was not set.

MessageOutcome Event (AMQP Component)

Fires when a message's outcome is available.

Syntax

type TMessageOutcomeEvent = procedure (
  Sender: TObject;
  const SessionName: String;
  SessionIndex: Integer;
  const LinkName: String;
  LinkIndex: Integer;
  const MessageId: String;
  Direction: Integer;
  State: Integer
) of Object;

property OnMessageOutcome: TMessageOutcomeEvent read FOnMessageOutcome write FOnMessageOutcome;

Remarks

This event fires whenever the outcome for a message (incoming or outgoing) is available.

SessionName is the name of the session the message was transmitted on.

SessionIndex is the index of the session in the Sessions collection property.

LinkName is the name of the link the message was transmitted on.

LinkIndex is the index of the link in the Links collection property.

MessageId is the Id of the message; it may be empty if a message Id was not set.

Direction indicates whether this outcome was sent (0) or received (1).

State indicates the actual message outcome. Possible values are:

• 0: Accepted - The message has been processed successfully.
• 1: Rejected - The message failed to process successfully. Includes an error describing why.
• 2: Released - The message has not been (and will not be) processed.
• 3: Modified - Same as "Released", but with additional metadata for the sender.

When State is Rejected (1), the RejectErrorCondition and RejectErrorDescription configuration settings can be queried before the event handler finishes to retrieve the error information.

When State is Modified (3), the ModifiedDeliveryFailed, ModifiedMessageAnnotations, and ModifiedUndeliverableHere configuration settings can be queried before the event handler finishes to retrieve the additional metadata.

SSLServerAuthentication Event (AMQP Component)

Fired after the server presents its certificate to the client.

Syntax

type TSSLServerAuthenticationEvent = procedure (
  Sender: TObject;
  const CertEncoded: String;
  const 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 (AMQP Component)

Fired when secure connection progress messages are available.

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.

AMQPLink Type

Represents an AMQP link.

Remarks

This type represents an AMQP link.

Fields

Constructors

constructor Create();

AMQPMessage Type

Represents an AMQP message.

Remarks

This type represents an AMQP message.

Fields

Constructors

constructor Create();

AMQPSession Type

Represents an AMQP session.

Remarks

This type represents an AMQP session.

Fields

Constructors

constructor Create();

Certificate Type

This is the digital certificate being used.

Remarks

This type describes the current digital certificate. The certificate may be a public or private key. The fields are used to identify or select certificates.

Fields

Constructors

>

constructor Create();

constructor Create(valEncoded: TBytes);

constructor Create(valStoreType: TiotCertStoreTypes; valStore: String; valStorePassword: String; valSubject: String);

constructor Create(valStoreType: TiotCertStoreTypes; valStore: TBytes; valStorePassword: String; valSubject: String);

Firewall Type

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 (AMQP Component)

AMQP Config Settings

{
  "type": "map",
  "value": [
    { "type": "symbol", "value": "key1" },
    { "type": "string", "value": "test" },
    { "type": "symbol", "value": "key2" },
    { "type": "int", "value": 100 }
  ]
}

TCPClient Config Settings

SSL Config Settings

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

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

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

Socket Config Settings

Base Config Settings

Trappable Errors (AMQP Component)

AMQP Errors

TCPClient Errors

SSL Errors

TCP/IP Errors