Regular readers of my blog are aware of the fact that I have written about this subject umpteen times earlier, and every time I have spoken about a new issue related to it. Few days ago, I had redone my local home network. I have LAN setup with wireless router connected with my four computers, two mobile devices, one printer and one VOIP solution. I had also formatted my primary computer and clean installed SQL Server 2008 into it. Yesterday, incidentally, I was sitting in my yard trying to connect SQL Server located in home office and suddenly I stumbled upon the following error. Finding the solution was the most infuriating part as it consumed my precious 10 minutes.
Let us look at few of the common errors received:
An error has occurred while establishing a connection to the server.
(provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 5)
An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 1326)
I eventually found the resolution to this error on this blog itself; so I was saved from hunting for the solution. I am sure there are a number of developers who had previously fixed this error while installing SQL Server 2008 or SQL Server 2005 but in due course forgot the right solution to this error. This is just a quick refresher. Make sure to bookmark this as you never know when you would need this solution.
Let us check into the steps to resolve this error.
1) SQL Server should be up and running.
Go to All Programs >> Microsoft SQL Server 2008 >> Configuration Tools >> SQL Server Configuration Manager >> SQL Server Services, and check if SQL Server service status is “Running”.
In addition, ensure that your remote server is in the same network. Run “sqlcmd -L” in your command prompt to ascertain if your server is included in your network list. You can even find tutorial for the same here SQL SERVER – Find All Servers From Local Network – Using sqlcmd – Detect Installed SQL Server on Network.
I have confronted numerous situations when these nerve-wracking errors crop up, and most of the time when I try to troubleshoot I notice that SQL Server services are neither running nor installed. If SQL Server is not installed as default instance SQL Server Browser should be running together with it; we will explore this further in Topic 5.
2) Enable TCP/IP in SQL Server Configuration
When two or more SQL Servers are connected across network they do all communication using TCP/IP. The default port of SQL Server installation is 1433. This port can be changed through SQL Server Configuration Manager. TCP/IP should be enabled for SQL Server to be connected.
Go to All Programs >> Microsoft SQL Server 2008 >> Configuration Tools >> SQL Server Configuration Manager >> Select TCP/IP
Right Click on TCP/IP >> Click on Enable
You must restart SQL Server Services for all the changes to take effect. Right click and go to menu properties to select location where default port of SQL Server can be changed.
3) Open Port in Windows Firewall
Windows Firewall is very efficacious in protecting the Operating system from all sorts of malicious attacks. By default, many of the ports and services are refrained from running by firewall. Time and again, SQL Server ports are not open in firewall as well. All the ports on which SQL Server is running should be added to exception and firewall should filter all the traffic from those ports. As described, by default SQL Server runs on port 1433, but if default port is changed then the new port should be added to exception. If SQL Server has named instance (another instance besides default instance) is installed, SQL Server browser should also be added to the exception, as described in Step 7.
Go to Control Panel >> Windows Firewall >> Change Settings >> Exceptions >> Add Port
Make the following entries in popup “Add a Port” and click OK.
Name : SQL
Port Number: 1433
Protocol: Select TCP
4) Enable Remote Connection
Enabling remote connection is another important, yet oft-neglected step that is frequently missed by database administrators while setting up SQL Server. If this feature is turned off SQL Server will function smoothly on local machine, but it will let another server connect to it remotely. By default this feature is ON in SQL Server 2008.
Right click on the server node and select Properties.
Go to Left Tab of Connections and check “Allow remote connections to this server”
5) Enable SQL Server Browser Service
If SQL Server is not installed as default instance but instead installed as named instance and also if there is no specific TCP/IP port configured, it will give rise to the error that is being discussed in this article. If SQL Server Browser service is enabled, it will allow the server to be connected through dynamic TCP/IP port. Enabling this service is a one-time process, as on enabling it once it will apply to all the instances installed on the same server.
Go to All Programs >> Microsoft SQL Server 2008 >> Configuration Tools >> SQL Server Configuration Manager >> SQL Server Browser
Right Click on SQL Server Browser >> Click on Enable
6) Create exception of sqlbrowser.exe in Firewall
As elucidated in Step 6, sqlbrowser service needs to be enabled for named instance. Windows Firewall may prevent sqlbrowser.exe to execute. So, it is imperative to add exception for the same in windows firewall.
Search for sqlbrowser.exe on your local drive where SQL Server is installed. Copy the path of the sqlbrowser.exe like C:\Program Files\Microsoft SQL Server\90\Shared\sqlbrowser.exe and create the exception of the file in Firewall, as delineated in Step 3.
7) Recreate Alias
It is getting quite common to create alias of SQL Server and use it in application. This will ensure that in future if any physical SQL Server has to be moved, it will not be required to change any code or connection string. You can simply create alias with the same name pointing to different SQL Server and it will start working instantaneously. I have observed that a couple of times due to internal error while recreating alias this error was fixed.
Go to All Programs >> Microsoft SQL Server 2008 >> Configuration Tools >> SQL Native Client 10.0 Configuration >> Aliases
Delete the alias that is giving problem and recreate it with identical parameters.
I have tried my best to include all the methods of fixing this error and if I have missed any, please leave a comment and I will be very glad to include them here. I have put in my effort to encompass this issue in one article that needs to be refereed when any connection error comes up.
Watch SQL in Sixty Seconds video to Resolve Connection Error:
[youtube=http://www.youtube.com/watch?v=1k00z82u4OI]
Reference : Pinal Dave (https://blog.sqlauthority.com)
658 Comments. Leave new
i check my sql server configuration manager there all my sql serrver services are running but but still same problem Object reference not set to an instance of an object”
It really worked for me , thank you so much.
Thanks for the tip.
This helped as the alias on my SQL Server 2008 R2 need to be recreated.
Hi Guys,
A few computers on my network can connect with the SQL server and a few computers are having this specific problem. So I am guessing the problem is with the system that cant connect instead of the server. I will really appreciate any help
Thank You
We had one workstation that got this error while no others did, we found that shortening the computer name to 15 characters fixed it. We had been warned about this NetBIOS limitation when setting the name, but ignored the error as NetBIOS protocols are not enabled – but it must have come into play somewhere as this was the only change that we made, unless something about leaving and rejoining the domain fixed it. BTW, our problem was that this machine could not connect to server outside of our subnet, even though the server was still on the same domain. Bottom line: It’s worth checking your computer name and shortening it to be 15 characters or less if it is longer than that.
For procedure to add a port to exception on a Windows 7 machine, refer to following URL:
https://support.microsoft.com/hub/4338813/windows-help
Smart Point to be remembered
Make sure SQL Server and SQL Server Browser are exempted by the firewall on the server machine. This is done by putting sqlservr.exe and sqlbrowser.exe as an exception in the windows firewall.
I just lost all my hair figuring it out, hope this helps others
Thank you for posting this informative article its very useful to me. Ithnk my blog is a bit related to yours.
Thanks Bro.. Its is Working Fine. Problem in SQL Server Browser is not Enabled and also, it is disabled the Start Button.
So, I checked in the Service Tab and Changed the Start Mode to “Automatic”.
Then in General Tab , I started the Service. It is Working Fine.
Hi Pinal,
I am getting the same error when connecting to SQL Server 2008 R2 from my WCF Service. I am using .NET SQLClient namespace.
The funny part is that there is one more ASMX Web Service which is able to connect to the same server. Also, I created a small .NET Winforms app to test the connection string and it is also able to connect to the same SQL Server.
This WCF Service reads the connection string from App.config and runs properly in DEV and TEST machines. However, I am facing this issue in the client’s environment and I do not have much control to try different things. Also, Names Pipes is disabled due to some reason and using TCP/IP is the only option.
I have tried the following to enforce a TCP/IP connection but got the same error:
1) Used IP address and Port instead of Server’s name.
2) Used “Data Source=tcp:ServerName” instead of “Data Source=tcp:ServerName”.
3) Used Network Library attribute in the connection string.
Any inputs would be greatly appreciated.
Thanks,
Ashish
Thank you very much!
i tried the port number and everything still getting the error number 40: I am new to SQL server and currently using SQL server 2012 on windows 8. please let me know how to fix this error. It has taken my lot of time.
Thanks
Thanks!
System.Data.SqlClient.SqlException (0x80131904): A connection was successfully established with the server, but then an error occurred during the login process. (provider: SSL Provider, error: 0 – The token supplied to the function is invalid)
System.ComponentModel.Win32Exception (0x80004005): The token supplied to the function is invalid
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.Open()
at Utilities.SqlHelper.ExecuteDataset(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters)
ClientConnectionId:a1f5685c-d849-4e8c-9301-c0203f3b8a8d
thanks a lot. One of my colleagues referred me this link. It solved my connection errors while I have tried to connect SQL Management studio from other systems. thanks a lot!!
Hi to everybody,
some clients can connect to server( to Db) but some clients can’t connect to server(to Db).
Thanks for your reply.
Thank you Dave! I ran into this problem when upgrading my replication publisher to SQL 2012. The SQL 2005 subscriber could not connect until I followed your steps to add incoming Windows firewall policies for UDP and TCP.
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)
Simply wanted to say THANKS! Solved my issue and saved lots of time!!