gtpc1m36Transmission Control Protocol/Internet Protocol

Socket User Exits

Socket user exits allow you to activate and deactivate socket applications, and verify remote clients. TCP/IP offload support provides the following user exits:

TCP/IP native stack support provides the following user exits:

See TPF System Installation Support Reference for additional information about the socket user exits.

Socket Accept for TCP/IP Offload Support

The socket accept for TCP/IP offload support user exit (C542) provides a centralized program to screen all connection requests before they are returned to the server application. C542 is entered each time the accept() API function call receives a connection request from a client by using TCP/IP offload support.

Socket Activation

The socket activation user exit is entered during system cycle-up and during ZCLAW ACTIVATE processing at or above CRAS state. This user exit activates socket server applications and is called for each TCP/IP offload device connected to the TPF system.

Socket Connect

The socket connect user exit is called during CLAW connect processing and allows Common Link Access to Workstation (CLAW) applications to be activated.

Socket Cycle-Up When Using TCP/IP Offload Support

The socket cycle-up TCP/IP offload support user exit is entered only once during system cycle-up after all active offload devices are connected to the TPF system. When the TPF system successfully issues the socket cycle-up user exit, this user exit activates server applications for all TCP/IP offload devices that are connected to the TPF system.

Following are the major differences between the socket activation user exit and the socket cycle-up user exit:

Socket Deactivation

The socket deactivation user exit is entered:

For each TCP/IP offload device disconnected from the TPF system, socket deactivation enters the socket deactivation user exit to deactivate socket applications associated with the TCP/IP offload device.

Socket System Error

The socket system error user exit is entered when a socket application must exit as a result of a system error.

TCP/IP Native Stack Support Accept Connection

The TCP/IP native stack support accept connection (UACC) user exit allows you to verify a remote client connection request. UACC is called when an accept or activate_on_accept request is made for a socket that uses TCP/IP native stack support.

Select TCP/IP Support

The select TCP/IP support (USOK) user exit is called whenever a TPF application issues the socket call to create a new socket and both TCP/IP offload support and TCP/IP native stack support are defined. USOK decides whether the socket being created will use TCP/IP offload support or TCP/IP native stack support. The default will be to use TCP/IP offload support.

Socket Cycle-Up When Using TCP/IP Native Stack Support

The socket cycle-up (CLCV) user exit is called once during system cycle-up and allows you to activate your socket server applications from a central point.