Heads up, you probably know the default port for SQL is 1433 but did you know the port is different for a named instance? And this port is dynamically set when you install the server. You can see what it is by looking in the registry. The below registry path is for SQL2008.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL10.(InstanceName)\MSSQLServer\SuperSocketNetLib\TCP\IPAll
There are more details in this article
And if you are using a named instance SQL server, don’t forget to adjust your connection string.
<add name=”MyConnString” connectionString=”Data Source=MyServerName, 51601; Initial Catalog=Northwind;user id=MyUserName;password=SecretPassword” providerName=”System.Data.SqlClient” />
Notice 51601 is the port number.