Unable to connect to any of the specified mysql hosts. C# MySQL

Question

I am getting the above error when I execute the code -

MySqlConnection mysqlConn=new MySqlConnection("server=127.0.0.1;uid=pankaj;port=3306;pwd=master;database=patholabs;");
        mysqlConn.Open();

I have tried setting server to localhost, user to root but I get the following error-

Error: 0 : Unable to connect to any of the specified MySQL hosts.
System.Transactions Critical: 0 : <TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Critical"><TraceIdentifier>http://msdn.microsoft.com/TraceCodes/System/ActivityTracing/2004/07/Reliability/Exception/Unhandled</TraceIdentifier><Description>Unhandled exception</Description><AppDomain>DBSync.exe</AppDomain><Exception><ExceptionType>MySql.Data.MySqlClient.MySqlException, MySql.Data, Version=6.7.4.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d</ExceptionType><Message>Unable to connect to any of the specified MySQL hosts.</Message><StackTrace>
at  MySql.Data.MySqlClient.NativeDriver.Open()
at MySql.Data.MySqlClient.Driver.Open()
at MySql.Data.MySqlClient.Driver.Create(MySqlConnectionStringBuilder settings)
at MySql.Data.MySqlClient.MySqlPool.CreateNewPooledConnection()
at MySql.Data.MySqlClient.MySqlPool.GetPooledConnection()
at MySql.Data.MySqlClient.MySqlPool.TryToGetDriver()
at MySql.Data.MySqlClient.MySqlPool.GetConnection()
at MySql.Data.MySqlClient.MySqlConnection.Open()
at DBSync.MainForm.BtnCalculateClick(Object sender, EventArgs e) in c:\Documents  and Settings\Test01\My Documents\SharpDevelop Projects\DBSync\DBSync\MainForm.cs:line 51
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message&amp;amp; m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message&amp;amp; m)
at System.Windows.Forms.ButtonBase.WndProc(Message&amp;amp; m)
at System.Windows.Forms.Button.WndProc(Message&amp;amp; m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&amp;amp; m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&amp;amp; m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG&amp;amp; msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at DBSync.Program.Main(String[] args) in c:\Documents and Settings\Test01\My Documents\SharpDevelop Projects\DBSync\DBSync\Program.cs:line 27</StackTrace><ExceptionString>MySql.Data.MySqlClient.MySqlException (0x80004005): Unable to connect to any of the specified MySQL hosts.
at MySql.Data.MySqlClient.NativeDriver.Open()
at MySql.Data.MySqlClient.Driver.Open()
at MySql.Data.MySqlClient.Driver.Create(MySqlConnectionStringBuilder settings)
at MySql.Data.MySqlClient.MySqlPool.CreateNewPooledConnection()
at MySql.Data.MySqlClient.MySqlPool.GetPooledConnection()
at MySql.Data.MySqlClient.MySqlPool.TryToGetDriver()
at MySql.Data.MySqlClient.MySqlPool.GetConnection()
at MySql.Data.MySqlClient.MySqlConnection.Open()
at DBSync.MainForm.BtnCalculateClick(Object sender, EventArgs e) in c:\Documents and Settings\Test01\My Documents\SharpDevelop Projects\DBSync\DBSync\MainForm.cs:line 51
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message&amp;amp; m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message&amp;amp; m)
at System.Windows.Forms.ButtonBase.WndProc(Message&amp;amp; m)
at System.Windows.Forms.Button.WndProc(Message&amp;amp; m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&amp;amp; m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&amp;amp; m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG&amp;amp; msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(Form mainForm)
at DBSync.Program.Main(String[] args) in c:\Documents and Settings\Test01\My Documents\SharpDevelop Projects\DBSync\DBSync\Program.cs:line 27</ExceptionString><DataItems><Data><Key>Server Error Code</Key><Value>1042</Value></Data></DataItems></Exception></TraceRecord>

I can connect to the mysql server through mysql workbench and query the database. It is only the code that doesn't work. Edit: I have noticed that the error crops up when I am using sharpdevelop and not when I am using Visual Studio.

Answer 1

Sometimes spacing and Order of parameters in connection string matters (based on personal experience and a long night :S)

So stick to the standard format here

Server=myServerAddress; Port=1234; Database=myDataBase; Uid=myUsername; Pwd=myPassword;

Answer 2

I am running mysql on a computer on a local network. MySQL Workbench could connect to that server, but not my c# code. I solved my issue by disconnecting from a vpn client that was running.

Answer 3

Since this is the top result on Google:

If your connection works initially, but you begin seeing this error after many successful connections, it may be this issue.

In summary: if you open and close a connection, Windows reserves the TCP port for future use for some stupid reason. After doing this many times, it runs out of available ports.

The article gives a registry hack to fix the issue...

Here are my registry settings on XP/2003:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\MaxUserPort 0xFFFF (DWORD)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\MaxUserPort\TcpTimedWaitDelay 60 (DWORD)

You need to create them. By default they don't exists.

On Vista/2008 you can use netsh to change it to something like:

netsh int ipv4 set dynamicport tcp start=10000 num=50000

...but the real solution is to use connection pooling, so that "opening" a connection really reuses an existing connection. Most frameworks do this automatically, but in my case the application was handling connections manually for some reason.

Answer 4

Update your connection string as shown below (without port variable as well):

MysqlConn.ConnectionString = 
    "Server=127.0.0.1;Database=patholabs;Uid=pankaj;Pwd=master;"

Hope this helps...