Reduce execution time of Socket handle inheritance tests (#31813)

Reduce the execution time for CtorAndAccept_SocketNotKeptAliveViaInheritance and DuplicateSocket_IsNotInheritable on Windows, using a new utility method, SocketTestExtensions.TryConnect().

src/libraries/Common/tests/System/Net/Sockets/SocketTestExtensions.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Threading;
+
 namespace System.Net.Sockets.Tests
 {
     internal static class SocketTestExtensions
@@ -49,5 +51,32 @@ public static (Socket, Socket) CreateConnectedSocketPair()
 
             return (client, server);
         }
+
+        // Tries to connect within the provided timeout interval
+        // Useful to speed up "can not connect" assertions on Windows
+        public static bool TryConnect(this Socket socket, EndPoint remoteEndpoint, int millisecondsTimeout)
+        {
+            var mre = new ManualResetEventSlim(false);
+            using var sea = new SocketAsyncEventArgs()
+            {
+                RemoteEndPoint = remoteEndpoint,
+                UserToken = mre
+            };
+
+            sea.Completed += (s, e) => ((ManualResetEventSlim)e.UserToken).Set();
+
+            bool pending = socket.ConnectAsync(sea);
+            if (!pending || mre.Wait(millisecondsTimeout))
+            {
+                mre.Dispose();
+                return sea.SocketError == SocketError.Success;
+            }
+
+            Socket.CancelConnectAsync(sea); // this will close the socket!
+
+            // In case of time-out, ManualResetEventSlim is left undisposed to avoid race conditions,
+            // letting SafeHandle's finalizer to do the cleanup.
+            return false;
+        }
     }
 }

src/libraries/System.Net.Sockets/tests/FunctionalTests/CreateSocketTests.cs

@@ -122,6 +122,9 @@ public void Ctor_Raw_NotSupported_ExpectedError(AddressFamily addressFamily, Pro
         [InlineData(false, 2)]
         public void CtorAndAccept_SocketNotKeptAliveViaInheritance(bool validateClientOuter, int acceptApiOuter)
         {
+            // 300 ms should be long enough to connect if the socket is actually present & listening.
+            const int ConnectionTimeoutMs = 300;
+
             // Run the test in another process so as to not have trouble with other tests
             // launching child processes that might impact inheritance.
             RemoteExecutor.Invoke((validateClientString, acceptApiString) =>
@@ -186,11 +189,13 @@ public void CtorAndAccept_SocketNotKeptAliveViaInheritance(bool validateClientOu
                                 listener.Dispose();
                                 using (var tmpClient = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
                                 {
-                                    Assert.ThrowsAny<SocketException>(() => tmpClient.Connect(ep));
-                                }
+                                    bool connected = tmpClient.TryConnect(ep, ConnectionTimeoutMs);
 
-                                // Let the child process terminate.
-                                serverPipe.WriteByte(42);
+                                    // Let the child process terminate.
+                                    serverPipe.WriteByte(42);
+
+                                    Assert.False(connected);
+                                }
                             }
                         }
                     }

src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketDuplicationTests.cs

@@ -167,11 +167,13 @@ public async Task DuplicateAndClose_TcpListener()
             Assert.Equal(TestMessage, receivedMessage);
         }
 
-        [OuterLoop] // long-running
         [PlatformSpecific(TestPlatforms.Windows)]
         [Fact]
         public void DuplicateSocket_IsNotInheritable()
         {
+            // 300 ms should be long enough to connect if the socket is actually present & listening.
+            const int ConnectionTimeoutMs = 300;
+
             // The test is based on CreateSocket.CtorAndAccept_SocketNotKeptAliveViaInheritance,
             // but contains simpler validation logic, sufficient to test the behavior on Windows
             static void RunTest()
@@ -202,10 +204,9 @@ static void ChildProcessBody(string clientPipeHandle)
                     listenerDuplicate.Dispose();
 
                     // Validate that we after closing the listening socket, we're not able to connect:
-                    SocketException ex = Assert.ThrowsAny<SocketException>(() => client.Connect(ep));
-                    Debug.Print(ex.Message);
-
+                    bool connected = client.TryConnect(ep, ConnectionTimeoutMs);
                     serverPipe.WriteByte(42);
+                    Assert.False(connected);
                 }
             }