The following types of WebSphere
MQ Telemetry Transport command
message have a payload in the message header:
- CONNECT
- The payload contains one or three UTF-8 encoded strings. The first string
uniquely identifies the client to the broker. The second string is the Will
topic, and the third string is the Will message. The second and third strings
are present only if the Will flag is set in the CONNECT Flags byte.
- SUBSCRIBE
- The payload contains a list of topic names to which the client can subscribe,
and the QoS level. These strings are UTF-encoded.
- SUBACK
- The payload contains a list of granted QoS levels. These are the QoS levels
at which the administrators for the broker have permitted the client to subscribe
to a particular Topic Name. Granted QoS levels are listed in the same order
as the topic names in the corresponding SUBSCRIBE message.
The payload part of a PUBLISH message contains application-specific
data only. No assumptions are made about the nature or content of the data,
and this part of the message is treated as a BLOB.
If you want an application
to apply compression to the payload data, you need to define in the application
the appropriate payload flag fields to handle the compression details. You
cannot define application-specific flags in the fixed or variable headers.