The PI-API writes error messages to the log file on each system. Under WINDOWS this file is called pipc.log and is located either in the PIHOME\DAT directory or in the WINDOWS temp directory. Specification of the PIHOME directory is discussed earlier under the discussion of the buffer file. Under UNIX the log file is called pimesslogfile and is found in the $PIHOME/dat directory.
Errors may be written to this file at any time and periodic inspection is recommended. In addition to errors, the starting and stopping of the buffering process is logged. The log file should be examined whenever the buffering process is started to ensure correct startup.
Error numbers found in this log correspond to messages that may be found in several sources. The System Errors topic lists common errors. Positive error values represent system errors and may be VMS errors (PI2 servers) or communication errors. When working with PI3 servers, large negative error numbers are returned starting at -10,000 and growing downwards. These errors can be translated using the pilogsrv utility file delivered with the PI-API.
It is also possible to receive errors from the protocol layer. In particular systems using WINSOCK implementations can receive errors in the range 10,000 to 11,005. These errors are associated in the log with messages describing socket connection, receive, or send errors and are thus discernible from the PI3 messages. Winsock errors are listed in the file winsock.h provided by the protocol stack vendor.