How to Quit() Unity application when using sockets?

Topic

How to "properly" terminate a client-server connection to prevent Unity freezing when Application.Quit() is called. I'm learning about sockets. This situation is new to me.

Problem description

For a long time I've had the issue of builds freezing upon exiting. I believe that a socket is not properly closed and preventing Unity from exiting correctly. I've come to this conclusion by elimination.

Situation

A method like the one below is used. This produce a freeze.

     public void Logoff()
     {
         try
         {
             if (serverSocket!= null)
             {
                 if (serverSocket.Connected)
                 {
                     serverSocket.Shutdown(SocketShutdown.Both);
                     serverSocket.Close();
                 }
             }
         }
         catch (Exception e)
         {
             print(e.ToString());
         }
         Application.Quit();
     }

Same code, but with an IEnumerator waiting for disconnection. However, the socket remains connected and Application.Quit() is never called.

     public void Logoff()
     {
         try
         {
             if (serverSocket!= null)
             {
                 if (serverSocket.Connected)
                 {
                     serverSocket.Shutdown(SocketShutdown.Both);
                     serverSocket.Close();
                 }
             }
         }
         catch (Exception e)
         {
             print(e.ToString());
         }
         StartCoroutine("Exiter");
     }

     IEnumerator Exiter()
     {
         while (serverSocket.Connected)
         {
             yield return null;
         }
         Application.Quit();
     }

Additional info

Server recognize a disconnect when closing the application from the task manager or when stopping 'play mode' in the Unity editor. I cannot produce a 'true' disconnect from code. Async client and server, AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp.