STOMP Component

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A simple but powerful STOMP client implementation.

Syntax

TiotSTOMP

Remarks

The STOMP component provides an easy-to-use STOMP client implementation that supports STOMP versions 1.1 and 1.2. The component supports both plaintext and TLS-enabled connections over TCP.

Connecting

Connecting to a STOMP server is easy; in the simplest case just call the ConnectTo method, passing the server's hostname and port number.

When connecting to a STOMP server, the component sends information from the following properties, if populated:

• IncomingHeartbeat
• OutgoingHeartbeat
• User
• Password

In addition to the above properties, the following configuration settings can be set before connecting (though in most cases this is not necessary):

• SupportedVersions: Controls which STOMP versions the component advertises support for.
• VirtualHost: Controls the virtual host to connect to. If left empty (default), the value from RemoteHost is used.

Subscriptions & Receiving Messages

When Subscribe is called, it will return a subscription Id. To unsubscribe, pass this subscription Id to the Unsubscribe method.

After subscribing to a message destination, any messages received will cause the MessageIn event to fire.

Basic Subscriptions Example stomp1.OnMessageIn += (s, e) => { Console.WriteLine("Received message from destination '" + e.Destination + "':"); Console.WriteLine(e.Data); }; string subId = stomp1.Subscribe("test/a/b", false); // Some time later... stomp1.Unsubscribe(subId);

Refer to Subscribe, Unsubscribe, and MessageIn for more information about subscriptions and receiving messages.

Sending Messages

To send messages, use the SendMessage and SendData methods. SendMessage is used to send messages with string payloads, while SendData is used to send messages with binary payloads.

Send String Message Example stomp1.SendMessage("test/a/b", "Hello, world!");

Send Binary Message Example byte[] fileContent = File.ReadAllBytes("C:\test\stuff.dat"); stomp1.SendData("test/a/b", fileContent);

Refer to SendMessage and SendData for more information about sending messages.

Using Transactions

STOMP transactions are used to group messages together for processing on the server. Messages sent as part of a transaction will not be delivered by the server until the transaction is committed. If the transaction is aborted, the server will discard the messages without attempting to deliver them.

Basic Transaction Example // Open a new transaction. stomp1.BeginTransaction("txn1"); // Set the Transaction property to make sure that messages are sent as part of the transaction. stomp1.Transaction = "txn1"; stomp1.SendMessage("test/a/b", "Hello, world!"); stomp1.SendMessage("test/a/b", "This is a test."); stomp1.SendMessage("test/a/b", "Another test!"); // At this point, none of the messages sent above would have been delivered to any clients // subscribed to the "test/a/b" destination yet, because the transaction is still open. // If we close and commit the transaction, the server will then deliver the messages to subscribers, // queue them, or process them in another manner; the behavior is server-dependent. stomp1.CommitTransaction("txn1"); // Or, the transaction can be aborted, in which case the server will discard the messages // without delivering them to the subscribers. //stomp1.AbortTransaction("txn1"); // Reset (or change) the Transaction property after committing or aborting a transaction // so that future messages are not associated with the previous transaction. stomp1.Transaction = "";

Refer to BeginTransaction for more information about using transactions.

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.

Connected Property (STOMP Component)

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.

When connecting to a STOMP server, the component sends information from the following properties, if populated:

• IncomingHeartbeat
• OutgoingHeartbeat
• User
• Password

In addition to the above properties, the following configuration settings can be set before connecting (though in most cases this is not necessary):

• SupportedVersions: Controls which STOMP versions the component advertises support for.
• VirtualHost: Controls the virtual host to connect to. If left empty (default), the value from RemoteHost is used.

This property is not available at design time.

ContentType Property (STOMP Component)

The content type of the outgoing message.

Syntax

property ContentType: String read get_ContentType write set_ContentType;

Default Value

'text/plain'

Remarks

This property is used to specify the content type (MIME type) for outgoing messages sent using SendMessage. The default value is text/plain, which should be sufficient is most cases.

Note that this property is ignored for messages sent using SendData, as such messages do not have a content-type header added to them. The absence of a content-type header indicates to the server that the data should be treated as a binary blob.

This property is not available at design time.

Firewall Property (STOMP 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.

Headers Property (STOMP Component)

User-defined headers added to outgoing messages.

Syntax

property Headers: TiotSTOMPHeaderList read get_Headers write set_Headers;

Remarks

This property holds a collection of STOMPHeader items representing user-defined headers. The headers in this collection are added to each outgoing message sent with SendMessage or SendData.

Note that the STOMP specification defines a number of standard headers necessary for implementing the STOMP protocol. When constructing an outgoing message, the component silently ignores any user-defined headers that are already set by the component.

This property is not available at design time.

IncomingHeartbeat Property (STOMP Component)

Specifies the server-to-component heartbeat timing.

Syntax

property IncomingHeartbeat: Integer read get_IncomingHeartbeat write set_IncomingHeartbeat;

Default Value

0

Remarks

This property specifies the incoming heartbeat interval, which is the number of seconds without any server-to-component communication that the server will allow to elapse before sending the component a heartbeat (keepalive). If set to 0 (default), incoming heartbeats are disabled.

For information about outgoing (component-to-server) heartbeats; see the OutgoingHeartbeat property.

Before Connecting

Before connecting, this property is used to specify the desired incoming heartbeat interval (in seconds). By default, this property is set to 0 (no heartbeat).

During the connection process, the incoming heartbeat interval requested by the component is compared to the minimum interval supported by the server, and the larger of the two values is selected. If one or both sides supply 0 as their value, then no server-to-component heartbeats will be sent.

After Connecting

After connecting, this property cannot be set. Instead, it reflects the incoming heartbeat interval agreed upon by the component and the server during the connection process.

As the incoming heartbeat interval negotiation notes above imply, it is possible that the agreed-upon incoming heartbeat interval may either be larger than what the component requested, or may be 0 (i.e., incoming heartbeats are disabled).

This property is not available at design time.

LocalHost Property (STOMP 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 (STOMP 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.

OutgoingHeartbeat Property (STOMP Component)

Specifies the component-to-server heartbeat timing.

Syntax

property OutgoingHeartbeat: Integer read get_OutgoingHeartbeat write set_OutgoingHeartbeat;

Default Value

0

Remarks

This property specifies the outgoing heartbeat interval, which is the number of seconds without any component-to-server communication that the component will allow to elapse before sending the server a heartbeat (keepalive). If set to 0 (default), outgoing heartbeats are disabled.

For information about incoming (server-to-component) heartbeats; see the IncomingHeartbeat property.

Before Connecting

Before connecting, this property is used to specify the minimum supported outgoing heartbeat interval (in seconds). By default, this property is set to 0 (no heartbeat).

During the connection process, the minimum outgoing heartbeat interval supported by the component is compared to the interval requested by the server, and the larger of the two values is selected. If one or both sides supply 0 as their value, then no component-to-server heartbeats will be sent.

After Connecting

After connecting, this property cannot be set. Instead, it reflects the outgoing heartbeat interval agreed upon by the component and the server during the connection process.

As the outgoing heartbeat interval negotiation notes above imply, it is possible that the agreed-upon outgoing heartbeat interval may either be larger than the component's supported minimum, or may be 0 (i.e., outgoing heartbeats are disabled).

This property is not available at design time.

ParsedHeaders Property (STOMP Component)

Headers parsed from incoming messages.

Syntax

property ParsedHeaders: TiotSTOMPHeaderList read get_ParsedHeaders;

Remarks

This property holds a collection of STOMPHeader items, representing both standard and user-defined headers parsed from incoming messages. It is populated each time the MessageIn event fires, and is cleared after the MessageIn event completes.

Note that the component collapses headers with duplicate key names by default for incoming messages, only keeping the first header for each unique key. This behavior can be controlled using the CollapseHeaders configuration setting.

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

Password Property (STOMP Component)

A password if authentication is to be used.

Syntax

property Password: String read get_Password write set_Password;

Default Value

''

Remarks

If this property is set when connecting, the component will send the password in the passcode header.

This property is not available at design time.

ReadyToSend Property (STOMP 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 SendData or 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.

RemoteHost Property (STOMP Component)

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 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.

By default the component will connect in plaintext. To enable SSL set SSLEnabled to True.

RemotePort Property (STOMP Component)

The port of the STOMP server (default is 61613). The default port for SSL is 61612.

Syntax

property RemotePort: Integer read get_RemotePort write set_RemotePort;

Default Value

61613

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.

RequestReceipts Property (STOMP Component)

Whether the component should request that the server provide message receipts.

Syntax

property RequestReceipts: Boolean read get_RequestReceipts write set_RequestReceipts;

Default Value

false

Remarks

This property is used to specify whether the component should request that the server send back confirmations (known as a "receipts" in STOMP terminology) when it receives messages from the component. This is done by adding a receipt header to the outgoing frame.

When this property is set to True, and a message is sent, the ReceiptOut event will fire immediately after the MessageOut event fires.

Note that, while this property only controls receipt requests for outgoing messages, the component is capable of requesting receipts for any outgoing frame type. Use this table to determine which API members control receipt request for each outgoing frame type (all are False by default):

Received Receipt Notes

When a receipt is received, the ReceiptIn event fires.

Note that receipts are cumulative, and a STOMP server is not required to send back discrete receipts for each frame it receives that has a receipt header. For example, if the component has sent four message frames with the following receipt header values (in chronological order):

1. SEND-3
2. SEND-4
3. SEND-5
4. SEND-6

This property is not available at design time.

SSLAcceptServerCert Property (STOMP 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 (STOMP 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 (STOMP 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.

This property is not available at design time.

SSLProvider Property (STOMP 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 (STOMP 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.

Subscriptions Property (STOMP Component)

Collection of current subscriptions.

Syntax

property Subscriptions: TiotSTOMPSubscriptionList read get_Subscriptions;

Remarks

This property holds a collection of STOMPSubscription items representing the component's current subscriptions.

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

Timeout Property (STOMP 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.

TransactionId Property (STOMP Component)

Specifies the Id of the transaction that outgoing messages are associated with.

Syntax

property TransactionId: String read get_TransactionId write set_TransactionId;

Default Value

''

Remarks

This property, if not empty, is used to specify which transaction outgoing messages sent using SendMessage or SendData are associated with.

This property must either be empty, or set to the Id of a currently open transaction. The OpenTransactions configuration setting can be queried at any time to retrieve a comma-separated list of currently open transactions' Ids.

Note that this property only affects outgoing messages. It is also possible to send a message acknowledgment as part of a transaction by setting the AckTransactionId configuration setting during the MessageIn event handler.

Refer to BeginTransaction for more information about transactions.

This property is not available at design time.

User Property (STOMP Component)

A username if authentication is to be used.

Syntax

property User: String read get_User write set_User;

Default Value

''

Remarks

If this property is set when connecting, the component will send the user in the login header.

This property is not available at design time.

AbortTransaction Method (STOMP Component)

Aborts an existing transaction.

Syntax

procedure AbortTransaction(Id: String);

Remarks

This method aborts a transaction previously started with BeginTransaction. Id identifies the transaction to abort.

The OpenTransactions configuration setting can be queried to obtain a list of currently-open transactions.

Refer to BeginTransaction for more information about transactions.

AddHeader Method (STOMP Component)

Adds a custom header to send with outgoing messages.

Syntax

procedure AddHeader(Key: String; Value: String);

Remarks

This method is used to add user-defined headers to the list of headers held by the Headers collection property.

When SendMessage or SendData is called, all headers in the Headers collection property are added to the outgoing message.

Note that the STOMP specification defines a number of standard headers necessary for implementing the STOMP protocol. When constructing an outgoing message, the component silently ignores any user-defined headers that are already set by the component.

BeginTransaction Method (STOMP Component)

Begins a new transaction.

Syntax

procedure BeginTransaction(Id: String);

Remarks

This method begins a new transaction using the specified Id, which must be unique. There is no limit to how many transactions may be open at any given time.

A transaction is a group of messages and message acknowledgments which are all processed atomically when the transaction is committed or aborted.

Messages sent in a transaction will not be delivered to clients subscribed to the messages' destinations until the transaction is committed.

Since it is possible for multiple transactions to be open at any given time, the TransactionId property is used to specify which transaction (if any) messages should be sent in. Similarly, message acknowledgments can be sent in a transaction by setting the AckTransactionId configuration setting during the MessageIn event handler.

The OpenTransactions configuration setting can be queried at any time to retrieve a comma-separated list of currently open transactions' Ids.

Basic Transaction Example // Open a new transaction. stomp1.BeginTransaction("txn1"); // Set the Transaction property to make sure that messages are sent as part of the transaction. stomp1.Transaction = "txn1"; stomp1.SendMessage("test/a/b", "Hello, world!"); stomp1.SendMessage("test/a/b", "This is a test."); stomp1.SendMessage("test/a/b", "Another test!"); // At this point, none of the messages sent above would have been delivered to any clients // subscribed to the "test/a/b" destination yet, because the transaction is still open. // If we close and commit the transaction, the server will then deliver the messages to subscribers, // queue them, or process them in another manner; the behavior is server-dependent. stomp1.CommitTransaction("txn1"); // Or, the transaction can be aborted, in which case the server will discard the messages // without delivering them to the subscribers. //stomp1.AbortTransaction("txn1"); // Reset (or change) the Transaction property after committing or aborting a transaction // so that future messages are not associated with the previous transaction. stomp1.Transaction = "";

CommitTransaction Method (STOMP Component)

Commits an existing transaction.

Syntax

procedure CommitTransaction(Id: String);

Remarks

This method commits a transaction previously started with BeginTransaction. Id identifies the transaction to commit.

The OpenTransactions configuration setting can be queried to obtain a list of currently-open transactions.

Refer to BeginTransaction for more information about transactions.

Config Method (STOMP 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 (STOMP Component)

Connects to the remote host.

Syntax

procedure Connect();

Remarks

This method connects to the remote host, specified by RemoteHost and RemotePort. Calling this method is equivalent to setting the Connected property to True.

By default the component will connect in plaintext. To enable SSL set SSLEnabled to True.

When connecting to a STOMP server, the component sends information from the following properties, if populated:

• IncomingHeartbeat
• OutgoingHeartbeat
• User
• Password

In addition to the above properties, the following configuration settings can be set before connecting (though in most cases this is not necessary):

• SupportedVersions: Controls which STOMP versions the component advertises support for.
• VirtualHost: Controls the virtual host to connect to. If left empty (default), the value from RemoteHost is used.

ConnectTo Method (STOMP Component)

Connects to the remote host.

Syntax

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

Remarks

This method connects to the remote host specified by the Host and Port parameters. Calling this method is equivalent to setting the RemoteHost property to Host, setting RemotePort to Port, and then setting the Connected property to True.

By default the component will connect in plaintext. To enable SSL set SSLEnabled to True.

When connecting to a STOMP server, the component sends information from the following properties, if populated:

• IncomingHeartbeat
• OutgoingHeartbeat
• User
• Password

In addition to the above properties, the following configuration settings can be set before connecting (though in most cases this is not necessary):

• SupportedVersions: Controls which STOMP versions the component advertises support for.
• VirtualHost: Controls the virtual host to connect to. If left empty (default), the value from RemoteHost is used.

Disconnect Method (STOMP 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 (STOMP 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 (STOMP 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.

Reset Method (STOMP Component)

This method will reset the component.

Syntax

procedure Reset();

Remarks

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

ResetHeaders Method (STOMP Component)

Clear the user-defined headers collection.

Syntax

procedure ResetHeaders();

Remarks

This method clears the Headers collection property.

SendData Method (STOMP Component)

Publishes a message with a raw data payload.

Syntax

procedure SendData(Destination: String; Data: TBytes);

Remarks

This method publishes a STOMP message with a raw data payload to the specified Destination. The MessageOut event will fire after the message has been sent.

The STOMP specification does not place any restrictions on Destination names. Instead, each STOMP server is free to define its own requirements for, and/or interpretations of, a Destination name; for example, a server might prohibit certain characters, require a specific format, or interpret some patterns in a special manner. Be sure to consult the documentation for your STOMP server to determine how to build proper Destination names.

In addition to the payload, the outgoing messages will include:

• All user-defined headers held by the Headers collection property.
• If the TransactionId property is populated, the transaction Id that it specifies (which associates the message with that transaction).

If RequestReceipts is enabled when this method is called, the component will request that the server send back a receipt to confirm it has received the message. Refer to RequestReceipts for more information.

Note that no content type is defined for raw data payload messages; so the ContentType property is ignored by this method.

Send String Message Example stomp1.SendMessage("test/a/b", "Hello, world!");

Send Binary Message Example byte[] fileContent = File.ReadAllBytes("C:\test\stuff.dat"); stomp1.SendData("test/a/b", fileContent);

SendMessage Method (STOMP Component)

Publishes a message with a string payload.

Syntax

procedure SendMessage(Destination: String; Message: String);

Remarks

This method publishes a STOMP message with a string payload to the specified Destination. The MessageOut event will fire after the message has been sent.

The ContentType property can be used to specify the content type of the payload. By default, ContentType is set to text/plain.

The STOMP specification does not place any restrictions on Destination names. Instead, each STOMP server is free to define its own requirements for, and/or interpretations of, a Destination name; for example, a server might prohibit certain characters, require a specific format, or interpret some patterns in a special manner. Be sure to consult the documentation for your STOMP server to determine how to build proper Destination names.

In addition to the payload, the outgoing messages will include:

• All user-defined headers held by the Headers collection property.
• If the TransactionId property is populated, the transaction Id that it specifies (which associates the message with that transaction).

If RequestReceipts is enabled when this method is called, the component will request that the server send back a receipt to confirm it has received the message. Refer to RequestReceipts for more information.

Send String Message Example stomp1.SendMessage("test/a/b", "Hello, world!");

Send Binary Message Example byte[] fileContent = File.ReadAllBytes("C:\test\stuff.dat"); stomp1.SendData("test/a/b", fileContent);

Subscribe Method (STOMP Component)

Subscribes to a message destination on the server.

Syntax

function Subscribe(Destination: String; RequireAcks: Boolean): String;

Remarks

This method is used to subscribe to the specified message Destination on the server. The Id of the subscription is returned.

Once subscribed, the Subscribed event will fire and an item will be added to the Subscriptions collection property. The MessageIn event will fire anytime a message is received for any subscription.

The STOMP specification does not place any restrictions on Destination names. Instead, each STOMP server is free to define its own requirements for, and/or interpretations of, a Destination name; for example, a server might prohibit certain characters, require a specific format, or interpret some patterns in a special manner. Be sure to consult the documentation for your STOMP server to determine how to build proper Destination names.

If the RequireAcks parameter is set to True, the server will expect the component to send it a message acknowledgment for each message it delivers as part of this subscription. (Refer to the MessageIn event for more information about sending message acknowledgments).

Basic Subscriptions Example stomp1.OnMessageIn += (s, e) => { Console.WriteLine("Received message from destination '" + e.Destination + "':"); Console.WriteLine(e.Data); }; string subId = stomp1.Subscribe("test/a/b", false); // Some time later... stomp1.Unsubscribe(subId);

Unsubscribe Method (STOMP Component)

Removes an existing subscription.

Syntax

procedure Unsubscribe(Id: String);

Remarks

This method removes an existing subscription identified by the given Id, unsubscribing the component from the destination associated with the subscription.

Once unsubscribed, the relevant item will be removed from the Subscriptions collection property and the Unsubscribed event will fire.

Basic Subscriptions Example stomp1.OnMessageIn += (s, e) => { Console.WriteLine("Received message from destination '" + e.Destination + "':"); Console.WriteLine(e.Data); }; string subId = stomp1.Subscribe("test/a/b", false); // Some time later... stomp1.Unsubscribe(subId);

Connected Event (STOMP 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 (STOMP 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 (STOMP 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 (STOMP Component)

Fired when a component or protocol error occurs.

Syntax

type TErrorEvent = procedure (
  Sender: TObject;
  ErrorCode: Integer;
  const Description: String;
  const Data: String;
  const DataB: TBytes
) 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.

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

STOMP Protocol Errors

When this occurs, ErrorCode will be 600, Description will reflect the value of the ERROR frame's message header, and Data will contain the body of the ERROR frame (if one is present).

The ErrorHeaders configuration setting will also be populated with the raw headers from the ERROR frame for the duration of the Error event handler.

Log Event (STOMP Component)

Fired 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.
• Acknowledgment: Information about outgoing message acknowledgments.
• Frame: Frame content logging.

MessageIn Event (STOMP Component)

Fired when a message has been received.

Syntax

type TMessageInEvent = procedure (
  Sender: TObject;
  const MessageId: String;
  const SubscriptionId: String;
  const Destination: String;
  const Data: String;
  const DataB: TBytes;
  const ContentType: String;
  var Ack: Boolean
) of Object;

property OnMessageIn: TMessageInEvent read FOnMessageIn write FOnMessageIn;

Remarks

This events fires whenever the component has received a message.

In addition to the message details exposed by the event parameters, the ParsedHeaders collection property is populated with the headers parsed from the message. When the MessageIn event handler exits, the parsed headers are cleared. The following parameters are available within this event:

• MessageId: The unique Id of the message.
• SubscriptionId: The subscription Id the message is associated with.
• Destination: The message destination on the server which the message originated from.
• Data: The message's payload.
• ContentType: The content type of the message (may be empty).
• Ack: Set to True or False to control whether the component should send back a positive (True, default) or negative (False) message acknowledgment.

Message acknowledgments are only sent back to the server for messages which require them. A positive acknowledgment indicates that the message has been accepted, while a negative acknowledgment represents that the message has been rejected.

The following two configuration settings are also relevant in the context of sending back message acknowledgments for incoming messages:

• The AckTransactionId configuration setting, if not empty, specifies a transaction Id to associate the message acknowledgment with. It can only be set during the MessageIn event handler, and will be reset when the event handler ends.
• The RequestAckReceipts configuration setting controls whether the component will request that the server confirm receipt of the message acknowledgment. It is False by default, and can be set at any time.

MessageOut Event (STOMP Component)

Fired after a message has been sent.

Syntax

type TMessageOutEvent = procedure (
  Sender: TObject;
  const Destination: String;
  const Data: String;
  const DataB: TBytes;
  const ContentType: String
) of Object;

property OnMessageOut: TMessageOutEvent read FOnMessageOut write FOnMessageOut;

Remarks

This event fires after a message has been sent using either SendMessage or SendData. The following parameters are available within this event:

• Destination: The destination the message was sent to.
• Data: The message's payload.
• ContentType: The content type of the message (always empty for messages sent with SendData).

ReadyToSend Event (STOMP Component)

Fired when the component is ready to send data.

Syntax

type TReadyToSendEvent = procedure (
  Sender: TObject
) of Object;

property OnReadyToSend: TReadyToSendEvent read FOnReadyToSend write FOnReadyToSend;

Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a call to SendData or SendMessage fails due to a WOULDBLOCK condition. The event is also fired immediately after a connection to the remote host is established.

ReceiptIn Event (STOMP Component)

Fires when the component receives a receipt from the server.

Syntax

type TReceiptInEvent = procedure (
  Sender: TObject;
  const ReceiptId: String
) of Object;

property OnReceiptIn: TReceiptInEvent read FOnReceiptIn write FOnReceiptIn;

Remarks

This event fires anytime the component receives a receipt (that is, a confirmation that the server has received one or more frames) from the server. The ReceiptId parameter reflects the value of the receipt-id header in the incoming RECEIPT frame.

Note that receipts are cumulative, and a STOMP server is not required to send back discrete receipts for each frame it receives that has a receipt header. For example, if the component has sent four message frames with the following receipt header values (in chronological order):

1. SEND-3
2. SEND-4
3. SEND-5
4. SEND-6

Refer to RequestReceipts for more information about receipts.

ReceiptOut Event (STOMP Component)

Fires when the component sends a STOMP frame that includes a 'receipt' header.

Syntax

type TReceiptOutEvent = procedure (
  Sender: TObject;
  const ReceiptId: String
) of Object;

property OnReceiptOut: TReceiptOutEvent read FOnReceiptOut write FOnReceiptOut;

Remarks

This event fires anytime the component sends any STOMP frame that includes a receipt header on it. The ReceiptId parameter reflects the value of the receipt header.

Having a receipt header on an outgoing frame indicates to the server that it should send back a receipt to confirm that it has received the frame (though it is not required to do so immediately; see ReceiptIn for details). Anytime the server sends back a receipt, the ReceiptIn event will fire.

Refer to RequestReceipts for more information about receipts.

SSLServerAuthentication Event (STOMP 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 (STOMP 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.

Subscribed Event (STOMP Component)

Fired when the component has subscribed to a message destination on the server.

Syntax

type TSubscribedEvent = procedure (
  Sender: TObject;
  const Id: String;
  const Destination: String;
  RequireAcks: Boolean
) of Object;

property OnSubscribed: TSubscribedEvent read FOnSubscribed write FOnSubscribed;

Remarks

This event fires each time the component has subscribed to a message destination on the server. The following parameters are available within this event:

• Id: The Id used to identify the subscription.
• Destination: The message destination on the server which the subscription is associated with.
• RequireAcks: Whether messages the component receives as a result of the subscription will require acknowledgments to be sent back to the server.

Unsubscribed Event (STOMP Component)

Fired when the component has unsubscribed from a message destination on the server.

Syntax

type TUnsubscribedEvent = procedure (
  Sender: TObject;
  const Id: String;
  const Destination: String
) of Object;

property OnUnsubscribed: TUnsubscribedEvent read FOnUnsubscribed write FOnUnsubscribed;

Remarks

This event fires each time the component has unsubscribed from a message destination on the server. The following parameters are available within this event:

• Id: The Id that was used to identify the subscription.
• Destination: The message destination on the server which the subscription was associated with.

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();

STOMPHeader Type

A STOMP header.

Remarks

This type represents a STOMP header.

Fields

Constructors

constructor Create();

constructor Create(valKey: String; valValue: String);

STOMPSubscription Type

A STOMP subscription.

Remarks

This type represents a STOMP subscription.

Fields

Config Settings (STOMP Component)

STOMP Config Settings

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 (STOMP Component)

STOMP Errors

TCPClient Errors

SSL Errors

TCP/IP Errors