gtpc1m35Transmission Control Protocol/Internet Protocol

TPF Socket Application Programming Interface (API) Support

Socket API support consists of:

Socket API Functions Using TCP/IP Offload Support

Socket API functions, which are issued by the socket application, enter socket API support to start the processing of the functions. If the socket is using offload support, socket API support either passes a return code back to the application or sends the function to the TCP/IP offload device to obtain the return code for the application.

If socket API support sends the function to the TCP/IP offload device, it builds a request in inter-user communication vehicle (IUCV) format and sends the function through the TPF CLAW device interface to the TCP/IP offload device, using Common Link Access to Workstation (CLAW) protocol. While it is waiting for the response from the TCP/IP offload device, socket API support issues EVNTC and EVNWC macros to suspend the ECB unless the function call was an activate_on_receipt. In the activate_on_receipt case, socket API support returns to the socket application after sending the function to the TCP/IP offload device.

If the function call issued to the TCP/IP offload device was not an activate_on_receipt, the return code from the TCP/IP offload device is passed to socket OPZERO by the TPF CLAW device interface. Socket OPZERO posts the suspended ECB to reactivate socket API support, which returns the return code back to the application. See TCP/IP Internals for additional information about the TCP/IP internals and see Socket Application Programming Interface Functions Reference for a complete description of the socket API calls.

Socket API Functions Using TCP/IP Native Stack Support

Socket API functions, which are issued by the socket application, enter socket API support to start the processing of the functions. If the socket is using TCP/IP native stack support, the function is processed locally by the TPF system. If the operation can be completed immediately or the socket is running in nonblocking mode, control is returned to the application without a loss of control. If the operation cannot be completed immediately and the socket is running in blocking mode, the application ECB is suspended until the function is completed successfully, fails, or times out.