On the AS/400, use the WRKRDBDIRE command to get a list of configured
RDBs. Locate the RDB entry in the list with *LOCAL remote location and
use option 5 (Display). If the remote location type is *IP, the port
number should be shown. If the port shown is *DRDA, it is using 446.
Additional info is available in the Distributed Database Programming book:
This site is also sometimes helpful when configuring DB2 Connect: