When writing an IMS™ TCP/IP client program, the programmer must follow conventions established by the IMS Listener and by the IMS Assist module (if used). This information describes the call sequences and input/output data formats to be used by the client program. For server programming, see How to write an IMS TCP/IP server program.

In this information, a "client" is typically a TCP/IP host that is requesting the services of an IMS message processing program (MPP). This is considered to be the normal case. However, in some situations, an MPP can start as a server and then (because it needs the services of another program) switch roles from server to client.

In this information, the client will be assumed to be the TCP/IP host and the server, the IMS MPP.