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Publication data

Publishers can include the publication data in the message, or they can refer to it.

 

Including data in the message

Publication data is usually appended to the Publish command message, following the NameValueString of the MQRFH header, as shown in Publication data. The characteristics of the data are defined in the Encoding, CodedCharSetId and Format fields of the MQRFH header. Alternatively, string data can be contained within the NameValueString.

 

Referring to data in the message

Publishers can make information available to subscribers directly, without going through the broker. The publisher needs to advertise the fact that it is publishing information about a topic, and that it is willing to receive direct requests for this information from subscribers.

There are two ways that a subscriber can find out about this information:

• From a publication received in a normal way.

  The publisher can use a normal publication to advertise the fact that it has more information about a topic (for example, a large file in several different formats). The publisher should also specify the topic name to be used (which could be the same, or different) and where the subscriber can find the information.

• From a subscription to the metatopics.

  The publisher can register with the broker specifying that it accepts direct requests for information about a topic. Subscribers that request information about publishers (metatopics) will discover the names of publishers who publish on this topic. See Metatopics for information about metatopics.

 

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