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Labeled Messages

A labeled message is like an ordinary Rendezvous message, except that it includes supplementary information, which CM transports can use for certified message delivery:

•	The correspondent name of the CM transport that sent the message.

•	A sequence number assigned by the sending CM transport.

•	A time limit, after which the sending program no longer expects its CM transport to certify delivery of the message.

Sending a Labeled Message

Any CM transport can send a labeled message by using the sending calls in the certified message delivery library layer (see Table 27).

Table 27 CM Send Calls 

C	tibrvcmTransport_Send() tibrvcmTransport_SendReply() tibrvcmTransport_SendRequest()
C++	TibrvCmTransport::send() TibrvCmTransport::sendReply() TibrvCmTransport::sendRequest()
Java	TibrvCmTransport.send() TibrvCmTransport.sendReply() TibrvCmTransport.sendRequest()
.NET	CMTransport.Send CMTransport.SendReply CMTransport.SendRequest

Receiving a Labeled Message

Two kinds of listening transport can receive labeled messages:

•	An ordinary transport listens by creating an ordinary listening event.

•	A CM transport listens by creating a CM listening event.

Ordinary Listener Transport

When an ordinary transport receives a labeled message, it presents it to the appropriate callback function as if it were an ordinary message. That is, it ignores the supplementary information that distinguishes a labeled message (the sender’s correspondent name and sequence number).

CM Listener Transport

When a CM transport receives a labeled message, its behavior depends on context:

•	If the CM listener transport is registered for certified delivery, it presents the supplementary information to the callback function.

•	If a CM listener transport is not registered for certified delivery with the sending CM transport, it presents the sending transport’s correspondent name to the callback function, but omits the sequence number.

In addition, if appropriate, the CM listener transport automatically requests that the sending transport register the listener for certified delivery. (See Discovery and Registration for Certified Delivery.)

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