Remote connection, OK, local connection fails

Hi folks,
My program connect perfectly from a remote computer. But same program cannot connect if I'm running it at the same maskin where the server is installed (express with tools)
I can open the database with the management tools with no problem.
Any help?
XP, sqlexpress2012. Firewall is off. All network is enabled. using port 12022 for IP ALL.

Can you post your error messages?

My program just says "cannot connect to the database" when I am running it locally on the server where MSSQL is installed. I can also connect easy with the Management tools running on local server. Its a bit strange how the program can connect remotely but not locally. I will debug the code and send you more info.

It might be referring to the server by a name / address that is resolved for remote connection, but is not resolved for local connection.