SQL Server Connection String with Port doesn't work

Question

The scenario: SQL Server 2014 Developer with default settings and connection port (1433), C# with Entity Framework 6.

Using SQL Server with EF6 in my C# app, the following connection string works like a charm:

Data Source=localhost;Initial Catalog =...

But this connection string fails:

Data Source=localhost,1433;Initial Catalog =...

Yes, this is the correct port.

Snooping around in the configurations of SQL Server I found a solution by activating the TCP/IP protocol, but, since it's the default port, isn't it supposed to work just like the other connection string without the port? Even with the TCP/IP deactivated (which is the default)?

Thanks!

It might be the case that it's communicating using named pipes in the first instance, but in the second instance since you're specify a port it's forcing it to use tcp/ip. — Dave Zych
– Dave Zych, Commented Sep 17, 2015 at 15:00
A client can't connect even to localhost if TCP/IP isn't enabled. localhost by itself worked because a different protocol was used, most likely Shared Memory. Only Shared Memory is enabled by default, which allows connections only from the local machine ie localhost. — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Sep 17, 2015 at 15:12
That´s right, people. Changing the localhost to an IP address prevents it from working too. The TCP/IP protocol is required for non-shared memory access. Wonder why it comes deactivated, maybe it´s default for the Developer version of SQL Server. Anyway, thanks! — MurariAlex
– MurariAlex, Commented Sep 17, 2015 at 17:00
In my experience the dev version defaults to TCP/IP disabled. Standard version does too, IIRC. — mikeb
– mikeb, Commented Sep 17, 2015 at 17:22

mikeb · Accepted Answer · 2015-09-17 15:01:00Z

5

You do actually specify the port like OP does, the 2 comments are wrong. https://www.connectionstrings.com/sql-server/

The reason you had to turn on TCP/IP is that you must enable TCP/IP for the server to listen on a port, default or otherwise.

The server, if TCP/IP is on, defaults to port 1433. If TCP/IP is not on, then by definition it cannot listen to any ports.

answered Sep 17, 2015 at 15:01

mikeb

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MurariAlex Over a year ago

Thanks, found out in the comments that the connection string without the port connects to the database via shared memory access, and you´re right, to listen to an specific port or even connect from another host, the TCP/IP protocol (that is used when the port is specified) has to be activated.

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