SQL Server Management Studio - connection with SQL Server database engine This question regards SQL Server 2005 and 2012.

I have a database server with two instances of SQL Server. Through SQL Server Management Studio I was able to connect to both instances by providing "IP-Address"\"InstanceName" and  user ID/password. But, I was not able to telnet the server on port 1433 from command prompt of the client PC.

Finally, when I specified TCP port 1433 through "SQL Server Configuration Manager" on the server and restart SQL Server services I was able to telnet to server on port 1433.

I want to know how "SQL Server Management Studio" was able to make a connection with SQL Server even if port 1433 was not active on SQL Server? And, the sequence of activities that takes place in background when Management Studio initiates connection with SQL Server?
The port 1433 is reserved for the default instance (MSSQLSERVER). When you have a named instance, where you can connect via "IP-Address"\"InstanceName", the port number is different. You can see the actual port number when you look into your SQL Server Logfile.