Unable to connect to any of the specified MySQL hosts.

[yukozh]

  An error occurred using the connection to database 'joyoi_mgmtsvc' on server '127.0.0.1'.

MySql.Data.MySqlClient.MySqlException (0x80004005): Unable to connect to any of the specified MySQL hosts.
at MySql.Data.Serialization.MySqlSession.d__52.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MySql.Data.MySqlClient.ConnectionPool.d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MySql.Data.MySqlClient.MySqlConnection.d__61.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MySql.Data.MySqlClient.MySqlConnection.d__14.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.d__34.MoveNext()

[yukozh]

I am using pomelo and mysqlconnector to build a service, but it will always throw this exception when the service started a period.

I am using the local MySQL 5.7 server.

[caleblloyd]

Can you connect from the command line client? This usually just means there is no MySQL server on that host/port

[caleblloyd]

If the service is running at system start maybe it's trying to connect before MySQL is ready. You could put a simple try/catch that tries to connect for 60 seconds and sleeps 1 second if it catches MySqlException in your startup logic

[yukozh]

workbench is ok, just the mysqlconnector cannot connect to the server

[yukozh]

It will work about 2~3h(from the service started) and then throw the unable to connect mysql server exception

[yukozh]

Closing this because we have also used the Docker.DotNet, They did not dispose http client and exhaust socket. (dotnet/Docker.DotNet#231)

[linehammer]

In some of the ways, spacing and the order of parameters in the MySql connection string does matters.

So stick to the standard format

MysqlConn.ConnectionString = "Server=yourServerAddress; Port=1234; Database=myourdb; Uid=uid; Pwd=pass;

If the above connection string fails, try update your c# mysql connection string as shown below (without port variable as well):

MysqlConn.ConnectionString = "Server=127.0.0.1;Database=yourdb;Uid=uid;Pwd=pass;"