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error: 26 - Error Locating Server/Instance Specified

Answered error: 26 - Error Locating Server/Instance Specified

  • Wednesday, February 10, 2010 9:56 AM
     
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    When trying to connect to a SQL server instance, I get this error:

    A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) (.Net SqlClient Data Provider)

    It happens with:

    • SQL Server Management Studio: 
      Microsoft SQL Server Management Studio      10.0.2531.0
Microsoft Analysis Services Client Tools      10.0.1600.22
Microsoft Data Access Components (MDAC)      6.1.7600.16385
Microsoft MSXML      3.0 4.0 5.0 6.0 
Microsoft Internet Explorer      8.0.7600.16385
Microsoft .NET Framework      2.0.50727.4927
Operating System      6.1.7600
    • ApexSQL Edit: 
      Version 2008.09.0168
    • My LINQ To SQL application

    However, Visual Studio 2008 can connect to this server/database:

    Microsoft Visual Studio 2008 

  Version 9.0.30729.1 SP 

  Microsoft .NET Framework 

  Version 3.5 SP1

Installed Edition: Enterprise

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  Version 9.0.30729.1

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    If I turn the client machine's (Windows 7 Enterprise x64) Firewall (Windows) for domain networks, all applications can connect successfully.

    I can successfully connect to many servers and databases in the same domain as this one without having to turn off the firewall. What's happening here?

    Paulo Morgado (http://PauloMorgado.NET/)
     

All Replies

  • Thursday, February 11, 2010 10:48 AM
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    Hi Paulo,
    Windows Firewall will block the TCP port on which your SQL Server instance is listening or connections with named pipes protocol. However you do not need to turn off your Windows Firewall, instead just add the TCP port to the Exception list of your Windows firewall. After than you should be able to connect to your SQL Server.

    You can first check your SQL Server instance's listening TCP port via Start->All Programs->Microsoft SQL Server 2008->Configuration Tools->SQL Server Configuration Manager->SQL Server Network Configuration->Protocols for MSSQLServer. Make sure that TCP/IP protocol is enabled. if not, enable it first and then restart your SQL Server service. Then double click TCP/IP protocol, switch to the IP Addresses and you can find the TCP port. By default it is 1433. Once you identified the TCP port, open your Windows Firewall and configure your firewall to allow the connection to the TCP port:
    Open a port in Windows Firewall
    http://windows.microsoft.com/en-us/windows-vista/open-a-port-in-windows-firewall

    Best regards,
    Charles Wang
    Please remember to mark the replies as answers if they help and unmark them if they provide no help
     
  • Thursday, February 11, 2010 2:32 PM
     
     
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    How can I know the TCP port given that I do not have any access to that SQL Server's Configuration Manager? The only information I have is:

    • server name
    • server instance
    • database name
    • user name
    • password

    Visual Studio 2008's Server Explorer can successfully connect and retrieve data. SQL Server 2008 Management Studio, ApexSQL Edit and my .NET application can't. Why is this a client firewall problem?

    Paulo Morgado (http://PauloMorgado.NET/)
     
  • Friday, February 12, 2010 10:03 AM
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    Hi Paulo,
    I had thought that it was a firewall issue at server side, however it looks that I misread your information now.

    I notice that you are using Windows 7 as the client on which the windows firewall has improved a lot. Please check if you ever define an outbound rule in your Windows firewall. Here are some articles for your reference:
    Create an Outbound Program or Service Rule on Windows 7, Windows Vista, Windows Server 2008 or Windows Server 2008 R2
    <!---->
    http://technet.microsoft.com/en-us/library/cc947786(WS.10).aspx
    Create an Outbound Port Rule on Windows 7, Windows Vista, Windows Server 2008 or Windows Server 2008 R2
    <!---->http://technet.microsoft.com/en-us/library/cc947789(WS.10).aspx
    Enable Predefined Outbound Rules on Windows 7, Windows Vista, Windows Server 2008, or Windows Server 2008 R2
    <!---->http://technet.microsoft.com/en-us/library/cc947820(WS.10).aspx

    Best regards,
    Charles Wang
    Please remember to mark the replies as answers if they help and unmark them if they provide no help
    • Proposed As Answer by JMaloney Sunday, June 26, 2011 4:25 PM
    •  
     
  • Friday, February 12, 2010 5:39 PM
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    The problem is not the server's TCP port (or at least, that's not the immediate problem). The error "SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified" specifically means that the client could not talk to the SQL Browser service on UDP port 1434. If removing the firewall fixes the problem, then opening up that specific port should resolve this particular error. You may then have to open the SQL Server TCP port, later, if you have different problems, but for now this will at least let you move forward.
     
  • Saturday, August 06, 2011 5:27 AM
     
     
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    Hi Charles,

     

    I tried to go to the place you have advised... how to switch to the IP Addresses and find the TCP port...

     

     

     

     

     

    Also. where is the place to add port in Firewall?