SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified

Question

Well i have a big problem that i'm trying for days to solve but i could not do it, so i need your help. I have a web application in asp.net 4.0 where i implemented custom membership and role providers. When i open the app homepage in it connects to the database and retrieves some information. There is also a login form and when i login it validates the user through the database and redirects me to the reserved pages but than this error appears:

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)

Description:

An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:

System.Data.SqlClient.SqlException: 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)

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

I tried many things, some solution i found in stackoverflow but nothing worked. Here are my connectionstrings:

<connectionStrings>
  <clear/>
  <remove name="LocalSqlServer"/>
     <add name="LocalSqlServer" connectionString="Data Source=MSSQL2008-1;Initial Catalog=agency;
        Integrated Security=False;User ID=adis_agency;Password=niarda2012;Connect Timeout=180;Encrypt=False;
        Packet Size=4096" providerName="System.Data.SqlClient" />
     <add name="AgencyConn" connectionString="Data Source=MSSQL2008-1;Initial Catalog=agency;
        Integrated Security=False;User ID=adis_agency;Password=niarda2012;Connect Timeout=180;Encrypt=False;
        Packet Size=4096" providerName="System.Data.SqlClient"/>
</connectionStrings>

Below are also the membership and role manager web.config section:

<membership defaultProvider="AuthProvider">
  <providers>
    <clear/>
      <add name="AuthProvider" type="AuthenticationProvider" applicationName="~/Reserved/" connectionStringName="AgencyConn"/>
  </providers>
</membership>
<roleManager enabled="true" defaultProvider="MyRoleProvider">
  <providers>
    <clear/>
      <add name="MyRoleProvider" type="RoleAccessProvider" connectionStringName="AgencyConn"/>
  </providers>
</roleManager>

Please can anybody help to figure out whats wrong?

Answer 1

If you are connecting from Windows machine A to Windows machine B (server with SQL Server installed), and are getting this error, you need to do the following:

On machine B:

1.) turn on the Windows service called "SQL Server Browser" and start the service

2.) in the Windows firewall, enable incoming port UDP 1434 (in case SQL Server Management Studio on machine A is connecting or a program on machine A is connecting)

3.) in the Windows firewall, enable incoming port TCP 1433 (in case there is a telnet connection)

4.) in SQL Server Configuration Manager, enable TCP/IP protocol for port 1433