RRSF uses z/OS® UNIX System Services APIs to start socket services. Whenever an error is encountered, a message is issued to the console. The message contains the service name, the return and reason code from the service, and an additional diagnostic code that helps IBM® service, if contacted. See z/OS UNIX System Services Messages and Codes for the return and reason codes. The return code is referred to as the errno, and the reason code is referred to as the errnojr. When looking up the reason code, use only the low-order halfword of the displayed value. In z/OS UNIX System Services Messages and Codes, there is a name and a value for each return code. Information about the identified service in z/OS UNIX System Services Programming: Assembler Callable Services Reference often lists some common errors by name and possible causes.

If the TCP socket listener encounters an error during initialization, or if a remote connection cannot be established, a console message is issued, and the attempt is periodically tried again. RRSF tracks the failing service name, including its return and reason code, and does not issue an error message if encountering the same error on a subsequent attempt.

Certain errors are not considered unrecoverable, and in such cases, RRSF does not issue an error message, but creates a LOGREC entry. These entries might be of value to IBM service when debugging a problem. See Creation of LOGREC data set entries for more information.