An example of a singleton rx observable that will notify when a socket is connected/disconnected

SocketWatcher.cs

public enum SocketStates
  {
    Unknown,
    Up,
    Down
  }

public class SocketWatcher : IObservable<SocketStates>, IDisposable
{
  private readonly BehaviorSubject<SocketStates> _socketState = new BehaviorSubject<SocketStates>(SocketStates.Unknown);
  private bool _running = true;

  public SocketWatcher(string host, int port)
  {
    Task.Run( async () =>
      {
        SocketStates prevState = SocketStates.Unknown;

        while ( _running )
        {
          var currState = await IsConnected( host, port );

          if (prevState != currState)
          {
            _socketState.OnNext( currState );
            prevState = currState;
          }
          
          await Task.Delay( 1000 );
        }
      } );
  }

  public void Dispose()
  {
    _running = false;
  }

  public IDisposable Subscribe( IObserver<SocketStates> observer )
  {
    return _socketState.Subscribe( observer );
  }

  public async static Task<SocketStates> IsConnected(string host, int port)
  {
    var tcpClient = new TcpClient();
    var cancelToken = new CancellationTokenSource( 1000 );

    await Task.Run( () => 
      {
        try
        {
          tcpClient.Connect( host, port );
        }
        catch (Exception)
        {

        }
      }, cancelToken.Token );

    return tcpClient.Connected ? SocketStates.Up : SocketStates.Down;
  }
}