foo.cs

		public async Task BeginListeningAsync (CancellationToken token)
		{
			var tcpListener = new Socket (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
			var tcp6Listener = new Socket (AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);

			using (tcpListener)
			using (tcp6Listener) {
				tcpListener.Bind (new IPEndPoint (IPAddress.Any, ListenPort));
				tcp6Listener.Bind (new IPEndPoint (IPAddress.IPv6Any, ListenPort));

				await Task.WhenAll (
					BeginListeningAsync (tcp6Listener, token),
					BeginListeningAsync (tcpListener, token)
				).ConfigureAwait (false);
			}
		}

		async Task BeginListeningAsync (Socket listener, CancellationToken token)
		{
			try {
				listener.Listen (10);
				using (token.Register (() => listener.Dispose ())) {
					while (!token.IsCancellationRequested) {
						var socket = await Task.Factory.FromAsync (listener.BeginAccept (null, null), listener.EndAccept).ConfigureAwait (false);
						ContextReceived (Catalog, socket, token);
					}
				}
			} catch (ObjectDisposedException ex) {
				if (!token.IsCancellationRequested) {
					Console.WriteLine (ex, "Unexpected ObjectDisposedException in BeginListeningAsync");
					throw;
				}
			} catch (OperationCanceledException) {
				// We cancelled successfully
			} catch (Exception ex) {
				Console.WriteLine (ex, string.Format ("Unhandled exception in BeginListeningAsync. {0}", listener.AddressFamily));
			}
		}

		static async void ContextReceived (Catalog catalog, Socket socket, CancellationToken token)
		{
			try {
				using (socket)
					Console.WriteLine ("Just disposing the socket");
			} catch (Exception ex) {
				socket.Close ();
				Console.WriteLine (ex, "The connection died. Oops!");
			}
		}