How does SQL Server host communicate with Client - what ports on both machines?

  • Question on Port configurations

    (please correct me if I'm wrong)

    - Default is 1433

    - We can change it to a specific port in sql config mgr

    - We can also allow dynamic ports, normally associated when using the named instances

    with UDP port 1434 on. In that case the client establishes a connection to a dynamic port

    - or we can define a specific port for each named instance

    How does communication work between client and host sql server?

    On the DB server what port does SQL Server use to communicate with the client side?

    (as mentioned the Client is configured on it's end to use 1433 for SQL)

    Client talks to SQL on port 1433 (for example server listening on port 1433)

    Is a random port from client given to SQL Server to use for 2 way communications?

    (e.g does Client give port 34567 to SQL or does SQL talk back to client .. and client uses port 1433 to communicate too)

    So would SQL talk on 34567 to client .. and client talk on port 1433 to server for 2-way communications?

    Thanks everyone!

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  • The client uses the RPC port range, so anything between TCP 1024 and 65535 to communicate to SQL on, its random as it depends what ports are already in use by the client.

    You can change the port of the SQL server service to any port you require, it doesn't have to be 1433, however if it is not 1433, you need UDP 1434 open so the browser can direct the client communication to the correct server port unless you specify in the connection string the port you require to connect on. EG SERVERNAME,2433

  • anthony.green (11/17/2015)


    The client uses the RPC port range, so anything between TCP 1024 and 65535 to communicate to SQL on, its random as it depends what ports are already in use by the client.

    You can change the port of the SQL server service to any port you require, it doesn't have to be 1433, however if it is not 1433, you need UDP 1434 open so the browser can direct the client communication to the correct server port unless you specify in the connection string the port you require to connect on. EG SERVERNAME,2433

    Got it! Thanks for helping with confirming the port range, much appreciated! Clear and concise info 🙂

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