In most cases, IMS™ server applications are started by the IMS Listener. Such programs are known as dependent programs because the Listener establishes the TCP/IP connection.

Under some circumstances, application design considerations require an application to establish its own connection between TCP/IP and IMS. For example, an IMS message processing program (MPP) might require the services of a UNIX processor that is connected through TCP/IP. An IMS application of this type is known as an independent program because it is not started by the Listener. Because independent programs do not use Listener services, they must define their own protocol.