Reusing SocketAsyncEventArgs for multiple calls to the static Socket.Connect()

[baulig]

Using the static Socket.Connect() multiple times with the same SocketAsyncEventArgs throws

  at System.Net.Sockets.SocketAsyncEventArgs.SetLastOperation (System.Net.Sockets.SocketAsyncOperation op) [0x00033] in /Workspace/mono-master/mcs/class/System/System.Net.Sockets/SocketAsyncEventArgs.cs:196 
  at System.Net.Sockets.SocketAsyncEventArgs.StartOperationWrapperConnect (System.Net.Sockets.MultipleConnectAsync args) [0x00000] in /Workspace/mono-master/mcs/class/System/System.Net.Sockets/SocketAsyncEventArgs.cs:245 
  at System.Net.Sockets.Socket.ConnectAsync (System.Net.Sockets.SocketType socketType, System.Net.Sockets.ProtocolType protocolType, System.Net.Sockets.SocketAsyncEventArgs e) [0x0007f] in /Workspace/mono-master/mcs/class/referencesource/System/net/System/Net/Sockets/Socket.cs:7877 
  at X.TestStaticConnect (System.Net.Sockets.SocketAsyncEventArgs e, System.String host, System.Int32 port) [0x00067] in <a3d5ba1db6c141f58c821248794a8daa>:0 
  at X.TestMultipleConnect (System.Boolean reuse) [0x00124] in <a3d5ba1db6c141f58c821248794a8daa>:0 
   --- End of inner exception stack trace ---

Simple example:

	static async Task TestMultipleConnect (bool reuse)
	{
		var port = 8888;
		var socket = new Socket (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
		socket.Bind (new IPEndPoint (IPAddress.Loopback, port));
		socket.Listen (3);

		ThreadPool.QueueUserWorkItem (_ => {
			var accepted = socket.Accept ();
			Console.WriteLine ($"ACCEPTED: {accepted.RemoteEndPoint}");

			accepted.Close ();

			var accepted2 = socket.Accept ();
			Console.WriteLine ($"ACCEPTED #1: {accepted2.RemoteEndPoint}");
		});

		var e = new SocketAsyncEventArgs ();
		await TestStaticConnect (e, "localhost", port).ConfigureAwait (false);
		Console.WriteLine ($"FIRST DONE!");

		if (!reuse)
			e = new SocketAsyncEventArgs ();

		await TestStaticConnect (e, "localhost", port).ConfigureAwait (false);
		Console.WriteLine ($"SECOND DONE!");
	}

	static Task TestStaticConnect (SocketAsyncEventArgs e, string host, int port)
	{
		var tcs = new TaskCompletionSource<object> ();

		e.Completed += (object sender, SocketAsyncEventArgs inner) => {
			Console.Error.WriteLine ($"COMPLETED: {inner.SocketError}");
			tcs.TrySetResult (null);
		};
		e.RemoteEndPoint = IPAddress.TryParse (host, out IPAddress address) ?
			(EndPoint)new IPEndPoint (address, port) :
			new DnsEndPoint ("localhost", port);
		Console.Error.WriteLine (e.RemoteEndPoint.AddressFamily);

		var ret = Socket.ConnectAsync (SocketType.Stream, ProtocolType.Tcp, e);
		Console.Error.WriteLine (ret);

		return tcs.Task;
	}

This works fine on .NET.

Full test case:
A.cs

This is a problem because the new System.Net.Http code from CoreFX is reusing SocketAsyncEventArgs instances.

[baulig]

You may have to run this on a Mac where localhost resolves to both ::1 and 127.0.0.1, with the IPv6 address being returned first - which seems to be the default these days.

[baulig]

There's another problem when using DnsEndPoint with socket.BeginConnect: see this new test.

1) Xamarin.WebTests.Console.Tests.SocketTests.BeginEndAsync.Run(True): Error

System.NotImplementedException: This method is not implemented by this class.
  at System.Net.EndPoint.Serialize () [0x00000] in /Workspace/mono-test/mcs/class/referencesource/System/net/System/Net/EndPoint.cs:40 
  at System.Net.Sockets.Socket.BeginSConnect (System.Net.Sockets.SocketAsyncResult sockares) [0x000ee] in /Workspace/mono-test/mcs/class/System/System.Net.Sockets/Socket.cs:1065 
  at System.Net.Sockets.Socket.BeginConnect (System.Net.EndPoint remoteEP, System.AsyncCallback callback, System.Object state) [0x00032] in /Workspace/mono-test/mcs/class/System/System.Net.Sockets/Socket.cs:986 
  at Xamarin.WebTests.SocketTests.BeginEndAsync.StartClient (Xamarin.AsyncTests.TestContext ctx, System.Net.EndPoint endPoint, System.Threading.CancellationToken cancellationToken) [0x0002d] in /Workspace/web-tests/Xamarin.WebTests.Tests/Xamarin.WebTests.SocketTests/BeginEndAsync.cs:90 
  at Xamarin.WebTests.SocketTests.SocketTestFixture+SocketConnection.Start (Xamarin.AsyncTests.TestContext ctx, Xamarin.WebTests.ConnectionFramework.IConnectionInstrumentation instrumentation, System.Threading.CancellationToken cancellationToken) [0x00086] in /Workspace/web-tests/Xamarin.WebTests.Tests/Xamarin.WebTests.SocketTests/SocketTestFixture.cs:168 
  at Xamarin.WebTests.TestRunners.ConnectionTestRunner.StartClient (Xamarin.AsyncTests.TestContext ctx, System.Threading.CancellationToken cancellationToken) [0x00001] in /Workspace/web-tests/Xamarin.WebTests.Framework/Xamarin.WebTests.TestRunners/ConnectionTestRunner.cs:87 
  at Xamarin.WebTests.ConnectionFramework.ClientAndServer.Initialize (Xamarin.AsyncTests.TestContext ctx, System.Threading.CancellationToken cancellationToken) [0x00103] in /Workspace/web-tests/Xamarin.WebTests.Framework/Xamarin.WebTests.ConnectionFramework/ClientAndServer.cs:108 
  at Xamarin.AsyncTests.Framework.Reflection.ReflectionFixtureInstance.Initialize (Xamarin.AsyncTests.TestContext ctx, System.Threading.CancellationToken cancellationToken) [0x0004c] in /Workspace/web-tests/Xamarin.AsyncTests.Framework/Xamarin.AsyncTests.Framework.Reflection/ReflectionFixtureInstance.cs:60 
  at Xamarin.AsyncTests.Framework.HeavyTestInvoker.SetUp (Xamarin.AsyncTests.TestContext ctx, Xamarin.AsyncTests.Framework.TestInstance instance, System.Threading.CancellationToken cancellationToken) [0x000e9] in /Workspace/web-tests/Xamarin.AsyncTests.Framework/Xamarin.AsyncTests.Framework/HeavyTestInvoker.cs:69 

[baulig]

Added some more tests to web-tests/Xamarin.WebTests.SocketTests.

[baulig]

Unfortunately, that doesn't fix the problem.