From 64048543af091941cd38c73c1e8e688c77c08015 Mon Sep 17 00:00:00 2001
From: Tom Deseyn <tom.deseyn@gmail.com>
Date: Thu, 30 Jan 2020 14:52:46 +0100
Subject: [PATCH] Support calling ConnectAsync for connectionless protocols

---
 .../src/System/Net/Sockets/Socket.cs                   | 10 +++++++++-
 .../System/Net/Sockets/SocketAsyncEventArgs.Unix.cs    |  3 +++
 .../System/Net/Sockets/SocketAsyncEventArgs.Windows.cs |  9 +++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs
index b93d08171590c..fab74cdd68d06 100644
--- a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs
+++ b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs
@@ -3779,7 +3779,15 @@ private bool ConnectAsync(SocketAsyncEventArgs e, bool userSocket)
                 SocketError socketError = SocketError.Success;
                 try
                 {
-                    socketError = e.DoOperationConnect(this, _handle);
+                    if (CanUseConnectEx(endPointSnapshot))
+                    {
+                        socketError = e.DoOperationConnectEx(this, _handle);
+                    }
+                    else
+                    {
+                        // For connectionless protocols, Connect is not an I/O call.
+                        socketError = e.DoOperationConnect(this, _handle);
+                    }
                 }
                 catch
                 {
diff --git a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Unix.cs b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Unix.cs
index ff3d37a54a47a..877f65a566b87 100644
--- a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Unix.cs
+++ b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Unix.cs
@@ -95,6 +95,9 @@ private void ConnectCompletionCallback(SocketError socketError)
             CompletionCallback(0, SocketFlags.None, socketError);
         }
 
+        internal unsafe SocketError DoOperationConnectEx(Socket socket, SafeSocketHandle handle)
+            => DoOperationConnect(socket, handle);
+
         internal unsafe SocketError DoOperationConnect(Socket socket, SafeSocketHandle handle)
         {
             SocketError socketError = handle.AsyncContext.ConnectAsync(_socketAddress.Buffer, _socketAddress.Size, ConnectCompletionCallback);
diff --git a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Windows.cs b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Windows.cs
index 29a0226031b74..08844f6799fa1 100644
--- a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Windows.cs
+++ b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.Windows.cs
@@ -272,6 +272,15 @@ internal unsafe SocketError DoOperationAccept(Socket socket, SafeSocketHandle ha
         }
 
         internal unsafe SocketError DoOperationConnect(Socket socket, SafeSocketHandle handle)
+        {
+            // Called for connectionless protocols.
+            SocketError socketError = SocketPal.Connect(handle, _socketAddress.Buffer, _socketAddress.Size);
+            FinishOperationSync(socketError, 0, SocketFlags.None);
+            Debug.Assert(socketError != socketError.IOPending);
+            return socketError;
+        }
+
+        internal unsafe SocketError DoOperationConnectEx(Socket socket, SafeSocketHandle handle)
         {
             // ConnectEx uses a sockaddr buffer containing the remote address to which to connect.
             // It can also optionally take a single buffer of data to send after the connection is complete.