A connection was successfully established with the server, but then an error occurred during the pre-login handshake

For me the solution is to kill zombie IIS express worker processes.

e.g. locate in Task Manager and end task.

![enter image description here][1]


[1]:

As described in the answer of [Ricardo][1] ,

netsh Winsock reset

has worked for me ,


[1]:

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**P.S.** if you have Internet download manager or such programs which changes you IP Setting is installed then after running this command when you reboot your computer IDM will ask to change setting , Set NO in this case and then run your application it will work correctly.

Hope it

I had a similar issue where I couldn't connect to a database and tried the recommendations here.

At the end of the day this is what worked for me:

Used the SQL Server Configuration Manager tool to enable the TCP/IP and/or the Named Pipes protocols on the SQL Server client computer.

1. Click Start, point to All Programs, and click SQL Server Configuration Manager.
2. Click to expand SQL Server Network Configuration and then click Client Protocols.
3. Right-click the TCP/IP protocol and then click Enable.
4. Right-click the Named Pipes protocol and then click Enable.
5. Restart the SQL server service if prompted to do so.

I am still not sure why or when this was disabled.

I experienced this error when running some very memory-expensive processes. When the system started to run short of memory, I begun to notice this kind of error.
I had to change the algorithm in order to make a better use of RAM.

To be noted that while some threads threw this exception, some other threw:

> System.Data.SqlClient.SqlException (0x80131904): Connection Timeout Expired. The timeout period elapsed while attempting to consume the pre-login handshake acknowledgement. This could be because the pre-login handshake failed or the server was unable to respond back in time. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=43606; handshake=560; ---> System.ComponentModel.Win32Exception (0x80004005): The wait operation timed out

Both problems disappeared after the system was changed so that it could run using less RAM.

Same problem here and no answers listed here worked, nor any solutions I could find online. The issue started shortly after Windows 10 anniversary update got applied on my dev PC and only affected my old SQL Server 2005 instance. I was not able to connect to the instance via my Web Applications or even using Sql Management Studio.

For what it's worth, this is what resolved it for me:

1. **Open SQL Server Configuration Manager** (depending on what version of SQL Server you're running):

- C:\Windows\SysWOW64\SQLServerManager.msc
- C:\Windows\SysWOW64\SQLServerManager10.msc OR
- C:\Windows\SysWOW64\SQLServerManager12.msc OR
- etc

2. **Select SQL Server Services**

3. **Locate the troubled service and view Properties**
- eg SQL Server (SQL2005) in my case


4. **In the Log On tab, change the "Built-in account" to "Network Service"**




Which is almost what this random solution said:

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I chose Network Service for no reason at all. Mine was already configured to use Local System. This security doesn't matter to me as it was only problematic on my Local development machine, only accessed locally. I can't advise why this works, but it did.

In my case, i was getting the error when i wanted to access a remote database. However, i solved it by starting SQL Server Browser service.

[![enter image description here][1]][1]


[1]:

Had the same problem from many days. I had to explicitly add TLS1.2 support in my core project to address this error and it worked fine. ( ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;)

See below link for more details (thanks to author Usman Khurshid)

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If you are connecting to an old SQL Server:

Switch from System.Data.**SqlClient.SqlConnection** to System.Data.**OleDb.OleDbConnection**

Use an OleDb connection string:

<connectionStrings>
<add name="Northwind" connectionString="Provider=SQLOLEDB.1; Data Source=MyServer; Initial Catalog=Northwind; Persist Security Info=True; User ID=abc; Password=xyz;" providerName="System.Data.OleDb" />
</connectionStrings>

In my case, [Re-enabling **TLS 1.0**][1] in the DB server resolved this issue.




[1]:

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Tried most of the above and nothing worked. Then turned off the VPN software (NordVPN) and everything was fine.