Hi,
I agree about the logging especially since it is a service. We did this type of socket programming for HIPAA messages. It also helps to hav a ntework guy on the AS400 side to watch the router to make sure your message is well constructed. If you are sending these messages to a CICS region you might need someone to see if your transaction meets the CICS format correctly. Also Threading is pretty much imperative when doing a service for your socket.

HTH
Bruce Carpenter
POD Inc. Albuquerque, New Mexico