Edit your log.ini and add the lines:
Code:
UCS__CLIENT=on
UCS__TRACE=on
Then restart the chatserver and login a character.
If the client is attempting to connect, you will see messages as it does so in the log for the UCS and also in the command window you have it running in.
If you see messages about chat/mail key not matching, then in your rules_values table, set Chat, EnableMailKeyIPVerification to false and restart everything and try again.
If you don't see messages in the chatserver window indicating your client is attempting to connect, then the only other thing I can suggest is to add a line to \windows\system32\drivers\etc\hosts on your client machine to map excal.dyndns.org to the internal address of your server.
You are correct that UDP 10234 needs forwarding on your firewall for people external to your network to be able to connect to the chatserver.