Why did a network-related or instance-specific error occur while establishing a connection to SQL Server

Question

I m very frustrated  I have a website running on Visual Web Developer 2008 Express with my local database  everything works great  I also have the same web site running on a production server  Everything was working great but tonight I did a  quot reset quot  on production   I deleted a couple of table  re-created them and inserted data  Everything was ok at this time   I deleted ALL the files via the FTP   I used the module called  quot Copy website quot  in visual studio and copy the site to the website via FTP    When I log on my website  here is the error I got   Server Error in     Application  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    Nothing has changed related to SQL connection  this is OLD code that I always used  My website is completely paralysed because of this and I feel sick inside because I feel there is nothing I can do  Can anyone help me please

User · Accepted Answer

Your connection string was probably overriden when you copied your new website version on the server  Please check the connection string in web config and see if it is valid

User · Answer

I had the same problem with SQL Server 2008 R2 and when I checked  SQL Server Configuration Manager  My SQL Server instance had Stopped  Right Clicking and Starting the Instance solved the issue

User · Answer

While u have tried tons of configuring and clicking and still facing the pop-up error  maybe my answer here will guide u to kill the error

User · Answer

My remote sql server was expecting connection at a different port and not on the default 1443   The solution was to add a     after your sql server IP and then add your port like so 129 0 0 1 2995  Check the       after server IP   Please find the image for reference below

User · Answer

I solved this issue by running the following command in an elevated command prompt as specified in this post   net start mssqlserver

User · Answer

In my case it was a very silly error  I was using a library to read the connection string out of a config file  and I forgot to double back slash   For example I had  localhost sqlexpress   which was read as localhostsqlexpress when I should rather have had localhost  sqlexpress note the

User · Answer

I recently had this problem and it ended up being a port issue  My production SQL Server was set up at to be port 1427 instead 1433   Just change the connection string to be     data source MySQLServerName 1427 initial catalog MyDBName      Hope this helps anyone who might be seeing this same issue

User · Answer

check forthe followings    Make sure your database engine is configured to accept remote connections      Start   All Programs   SQL Server 2005   Configuration Tools   SQL Server Surface Area Configuration     Click on Surface Area Configuration for Services and Connections     Select the instance that is having a problem   Database Engine   Remote Connections     Enable local and remote connections     Restart instance   Check the SQL Server service account       If you are not using a domain account as a service account  for example if you are using NETWORK SERVICE   you may want to switch this first before proceeding   If you are using a named SQL Server instance  make sure you are using that instance name in your connection strings in your ASweb P NET application       Usually the format needed to specify the database server is machinename instancename     Check your connection string as well

User · Answer

I had the same error  and it turned out  NET created a database on localhost which I wasn t aware of  When I tried to get the site live it didn t create the database  so the code was pointing to a database that was non existent   Hopefully this might help some other people out trying to troubleshoot

User · Answer

the cause is that SQL SERVER is stopped from services msc a solution for this problem could be starting SQL SERVER from services msc

User · Answer

I had the same problem but found that it was because the password for my Service Account for the Database Engine had expired   The solution was to login to that account  fix this  then set the account so password never expires

User · Answer

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    Turn on the Windows service called  SQL Server Browser  and start the service  In 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  enable incoming port TCP 1433  in case there is a telnet connection    In SQL Server Configuration Manager    enable TCP IP protocol for port 1433

User · Answer

we have to  enable TCP IP property in sql server configuration manager

User · Answer

If your server was working and suddenly started erroring out  your server instance stopped and connection settings were changed somehow   For SQL Server 2008 here is how you can fit this      Goto Start  gt  All Programs  gt  SQL Server 2008  gt  Configuration Tools  gt  SQL Server Configuration Manager  gt  SQL Server Services  And here you ll see all the instances and their state  The state of the instance you were trying to connect can be stopped here  Double click on the instance and then click on connect   It will connect and now go back and run your application  you will be able to connect with no error     This solution assumes the error is not being caused by something wrong in your connection string

User · Answer

I ve resolved the issue  It was due to the SQL browser service    Solution to such problem is one among below -   Check the spelling of the SQL Server instance name that is specified in the connection string  Use the SQL Server Surface Area Configuration tool to enable SQL Server to accept remote connections over the TCP or named pipes protocols  For more information about the SQL Server Surface Area Configuration Tool  see Surface Area Configuration for Services and Connections  Make sure that you have configured the firewall on the server instance of SQL Server to open ports for SQL Server and the SQL Server Browser port  UDP 1434   Make sure that the SQL Server Browser service is started on the server    link - http   www microsoft com products ee transform aspx ProdName Microsoft SQL Server amp EvtSrc MSSQLServer amp EvtID -1

User · Answer

I had same problem regarding that i e A network-related or instance-specific error occurred while establishing a connection to SQL Server   I was using SQL Server 2005    sqlexpress   and worked fine but suddenly  services stopped and gave me error   I solved it like this      Start -  Search Box -   Sql Configuration Manager -  SQL Server 2005 Services  and just Change Your SQL Server  SQLEXPRESS  State to Running by right clicking that service Sate

[.net] Why did a network-related or instance-specific error occur while establishing a connection to SQL Server?

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