Find the port SQL Server is running

 By default the TCP Port for SQL Server is 1433 , and the USD connection is 1434 . If you have a named instance the TCP port is configured dynamically .

You can find out this information by going to the registry and looking up TCP settings.

SQL 2005
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.<InstanceNumber>\MSSQLServer\
SuperSocketNetLib\TCP\

SQL 2008
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL10.<InstanceName>\MSSQLServer\
SuperSocketNetLib\TCP\

An alternate easier way would be the SQL Server Configeration Manager UI

Go to Windows > Start > SQL Server Program Folder > SQL Server Configuration Manager > SQL Server Network Configurations >  Protocols for your SQL Server > TCP/IP and right click the link.