Communicating with programs running in the TSO/E address spaces

A z/OS® UNIX message queue is the mechanism the CEA TSO/E address space manager uses for allowing communications between the caller and TSO/E, ISPF, and other programs running in the TSO/E address space. To communicate with the TSO/E address space, callers must read data from and write data to the message queue.

The CEA TSO/E address space manager creates a z/OS UNIX message queue for each TSO/E address space when the TSO/E address space is started, and anchors the message queue in the session table for the duration of the session. The CEA TSO/E address space manager deletes the message queue when the TSO/E address space ends.

Messages that typically are written to a 3270-type terminal are translated to UTF-8, converted to a JSON format, and written to the z/OS UNIX message queue along with identifying header information and a message type identifier. For a list of the message type identifiers, see Table 1.

Table 1. Message type identifiers
Message Type ID	Description
1	Control data for the client.
2	TSO/E data for the client.
3	ISPF data for the client.
4 thru 32768	Reserved for IBM®.
32769	Control TSO/E data from the client.
32770	TSO/E data from the client.
32771	ISPF data from the client.
32772 thru 65535	Reserved for IBM.
65536 and above	Available for use by applications.

For information about the JSON format used for TSO/E messages, see JSON format for TSO/E messages. For the JSON format used for ISPF messages, see the topic about JSON data structures and variables used to communicate between ISPF and a client in &f54sg00;.