TCP/IP provides a trace facility that can be helpful in diagnosing problems in applications using the CALL instruction API. The trace is implemented using the TCP/IP Component Trace (CTRACE) SOCKAPI trace option. The SOCKAPI trace option allows all Call instruction socket API calls issued by an application to be traced in the TCP/IP CTRACE. The SOCKAPI trace records include information such as the type of socket call, input, and output parameters and return codes. This trace can be helpful in isolating failing socket API calls and in determining the nature of the error or the history of socket API calls that might be the cause of an error. For more information about the SOCKAPI trace option, see z/OS Communications Server: IP Diagnosis Guide.