Commands | AMQP1 Sender Links

In the AMQP 1.0.0 protocol, a Sender Link is a communication channel established between an AMQP client and an AMQP server for the purpose of sending messages. It operates within the context of an AMQP session, which represents a logical channel for communication between the client and server.

 

Create Sender Link

To Create a new Sender Link, call the method CreateSenderLink which contains the following parameters:

 

• Session: the session name where the sender link will be attached.
• Name: (optional) the name of the sender link, if is not set, a random name will be assigned automatically.
• Target: (optional) you can specify the destination where messages should be received on the remote host by setting the "target" parameter. However, in certain scenarios, specifying the target may not be required. In such cases, providing an empty string will be sufficient.
• SndSettleMode: (mixed by default) AMQP offers the capability to discuss delivery assurances via the Message Settlement mechanism. Upon establishing a link, both the sender and the receiver discuss and agree upon a settlement mode (one for each role). Senders operate within one of these modes:

  • amqp1ssmSettled: The message is considered successfully delivered and acknowledged once it's sent.

  • amqp1ssmUnsettled: The message is not considered settled until it's explicitly accepted or rejected by the receiver. This allows for more control over message processing and handling.

  • amqp1ssmMixed: A combination of settled and unsettled modes can be used within a single AMQP session. Use the MessageOptions parameter of the SendMessage method to configure if the message is Settled or not.

 

When the Sender Link has been created successfully, the event OnAMQPLinkOpen will be fired.

 

oAMQP1.CreateSenderLink('MySession', 'MySenderLink');
procedure procedure TfrmClientAMQP1.AMQP1AMQPLinkOpen(Sender: TObject; const aSession: TsgcAMQP1Session; const aLink: TsgcAMQP1Link; const aAttach: TsgcAMQP1FrameAttach);
begin
  ShowMessage('#link-open: ' + aLink.Name);
end;

 

Await Create Sender Link

 

By default, the CreateSenderLink method is Asynchronous, so after calling the method, the code continue. If you want to wait till the CreateSenderLink method is completed and the confirmation sent by the server is received, set the property Await to True in the Options parameter.

 

procedure CreateSenderLink(const aSession, aSender: string);
var
  oOptions: TsgcAMQP1MethodOptions_CreateSenderLink;
begin
  oOptions := TsgcAMQP1MethodOptions_CreateSenderLink.Create;
  Try
    oOptions.Await := True;
    AMQP1.CreateSenderLink(aSession, aSender, '', oOptions);
  Finally
    oOptions.Free;
  End;
end;

 

Sending Messages

To Send a new Message, call the method SendMessage which contains the following parameters:

 

• Session: name of the session.
• Link: name of the sender link.
• Text: the text of the string message.

 

oAMQP1.SendMessage('MySession', 'MySenderLink', 'My first AMQP Message');

 

Sending Messages Mixed Mode

When the Sender Link is created in Mixed mode (the default), when sending a message, the user can set if want the message is settled or not. Use the MessageOptions parameter to define if the message is settled or not.

 

oMessageOptions := TsgcAMQP1MessageOptions.Create;
Try
  oMessageOptions.Settled := True;
  oAMQP1.SendMessage('MySession', 'MySenderLink', 'MyMessage', 'message-id', oMessageOptions);
Finally
  oMessageOptions.Free;
End;

 

Close Sender Link

To Close an existing Sender Link, call the method CloseLink which contains the following parameters:

 

• Session: name of the session that contains the link.
• Link: name of the sender link.
• Error: (optional) here you can set the reason why the link is closed.

 

When the Sender Link has been closed successfully, the event OnAMQPLinkClose will be fired.

oAMQP.CloseLink('MySession', 'MySenderLink');
procedure OnAMQPLinkCloseEvent(Sender: TObject; const aSession: TsgcAMQP1Session; const aLink: TsgcAMQP1Link; const aDetach: TsgcAMQP1FrameDetach);
begin
  ShowMessage('#link-close: ' + aLink.Name);
end;

Await Close Sender Link

 

By default, the CloseLink method is Asynchronous, so after calling the method, the code continue. If you want to wait till the CloseLink method is completed and the confirmation sent by the server is received, set the property Await to True in the Options parameter.

 

procedure CloseSenderLink(const aSession, aSenderLink: string);
var
  oOptions: TsgcAMQP1MethodOptions_CloseLink;
begin
  oOptions := TsgcAMQP1MethodOptions_CloseLink.Create;
  Try
    oOptions.Await := True;
    AMQP1.CloseLink(aSession, aSenderLink, oOptions);
  Finally
    oOptions.Free;
  End;
end;