Call sequence for the IMS Listener

Although you will probably not be writing a Listener program, it is important that you match the sequence of calls issued by the Listener when you write your client program. The Listener call sequence is:

INITIALIZE LISTENER
INITAPI: Connect the Listener to MVS™ TCP/IP at Listener startup. (This call is used only in programs written to the Sockets Extended interface.
SOCKET: Create a socket descriptor.
BIND: Allocate the local port for the socket. This port is used by clients when requesting connection to IMS™.
LISTEN: Create a queue for incoming connections.
WAIT FOR CONNECTION REQUEST
SELECT: Wait for an incoming connection request.
ACCEPT: Accept the incoming connection request; create a new socket descriptor to be used by the server for this specific connection.
READ: Read TRM; determine the IMS TRANCODE.
CHNG: Change the modifiable alternate PCB to reflect the desired IMS TRANCODE.
INQY: Ensure the desired IMS TRANCODE is available for scheduling.
ISRT: Use the alternate PCB to insert the transaction initiation message (TIM) and pass control information and user input data to the server.
GIVESOCKET: Pass the newly created socket to the server.
SYNC: Schedule the requested transaction.
SELECT: Wait for the server to take the socket.
CLOSE: Release the socket.
END OF CONNECTION REQUEST
: Return to "WAIT FOR CONNECTION REQUEST"
SHUTDOWN LISTENER
CLOSE: Close the socket through which the Listener receives connection requests from MVS TCP/IP.
TERMAPI: Disconnect the Listener from MVS TCP/IP before shutting down.