A little background:
I have a Windows .NET application that is in use by approximately 40 field employees across North America. This program allows the users to enter data while in the field (away form internet access) and then synchronizes to our Sql Server 2005 database at night. A couple days ago, two of my users reported getting the following error when they performed an action that would attempt to connect to our server database (which uses .NET's SqlConnection class).
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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Our field employees are typically operating on a hotel Wi-Fi connection, and at first I thought that they both coincidentally got on an "uncooperative" network the same day. The following day, having moved to different hotels, the problem went away for one of these users, but continued for the other.
Besides providing the error message, the purpose of this background is to point out that
- this is the first time this issue has occurred in over a year of using this software, and
- the majority of our users aren't having any problem connecting to our server database with the same software.
This makes me hesitate to think that the issue is at the server (most forums and blogs I've read on this error provide steps to ensure the SQL Server is configured properly).
Noticing the Named Pipes Provider portion of the error message, I guessed that maybe this user's computer or network was causing it to attempt connection via pipes rather than TCP, so I did try configuring the server to allow BOTH TCP/IP and Named Pipes for remote connections, where it was previously set to TCP/IP only. The error continued for this one user after changing this setting.
So now I'm left to brainstorm about what could be special about this one user's computer / software / internet connection that would hinder it from being able to connect to our SQL Server.
Our connection string does use our server's URL (not IP address), and I wondered if his laptop was having problems finding it by that address. However, he was able to access a website hosted from the same URL, so I guess the problem is somewhere else.
Any ideas would be greatly appreciated. Thanks!