My problem is related to the RFC_ERROR_COMMUNICATION question... I have a similar problem, and the error message I receive is:
(102) RFC_ERROR_COMMUNICATION: Connect to message server failed.
The error description is: Internal error.
We are using a JSP application with WebLogic on Solaris, to connect to SAP 4.0B. JCo 1.1
The application worked fine for a couple of hours, and then it cannot connect to SAP any more. And we receive the described error message. Thanks for any help.
Firstly, please upgrade to JCo 2.0.5 (although this will probably not fix your problem). Secondly, look for a file called DEV_RFC.TRC or similar and send it to SAP.