Hello,
I catch this exception all the time, when server has connection or no connection to client.
it is from the line of listeningSocket.Shutdown(SocketShutdown.Both);

the server is turned off but exception is still happen at this line.
Please support to check and update.
Thank you.

`System.Net.Sockets.SocketException
HResult=0x80004005
Message=A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied.
Source=System.Net.Sockets
StackTrace:
at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, String callerName)
at System.Net.Sockets.Socket.Shutdown(SocketShutdown how)
at lib60870.CS104.Server.Stop() in D:\work\C#\iec104\lib60870.NET\lib60870\CS104\Server.cs:line 943

This exception was originally thrown at this call stack:
[External Code]
lib60870.CS104.Server.Stop() in Server.cs`