Add ListenHandleTests (#1923)

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/ListenHandleTests.cs

@@ -0,0 +1,40 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Net;
+using System.Net.Sockets;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Server.Kestrel.Core;
+using Microsoft.AspNetCore.Testing;
+using Microsoft.AspNetCore.Testing.xunit;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
+{
+    [OSSkipCondition(OperatingSystems.Windows, SkipReason = "Listening to open TCP socket and/or pipe handles is not supported on Windows.")]
+    public class ListenHandleTests
+    {
+        [ConditionalFact]
+        public async Task CanListenToOpenTcpSocketHandle()
+        {
+            using (var listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                listenSocket.Bind(new IPEndPoint(IPAddress.Loopback, 0));
+
+                using (var server = new TestServer(_ => Task.CompletedTask, new TestServiceContext(), new ListenOptions((ulong)listenSocket.Handle)))
+                {
+                    using (var connection = new TestConnection(((IPEndPoint)listenSocket.LocalEndPoint).Port))
+                    {
+                        await connection.SendEmptyGet();
+
+                        await connection.Receive(
+                            "HTTP/1.1 200 OK",
+                            $"Date: {server.Context.DateHeaderValue}",
+                            "Content-Length: 0",
+                            "",
+                            "");
+                    }
+                }
+            }
+        }
+    }
+}