Http Proxy Improvements

Bug: proxy connect packet is malformed due to a space after HTTP/1.1.
Feature: Pass the host name so proxy host acls can be matched.
Feature: Switch to the WebRequest.DefaultWebProxy which allows for overriding in app.settings file and falls back to the system proxy if not configured.
Improvement: Use ordinal comparision for IndexOf on the proxy response.

Resolves #742 (original PR, this is a rebase)

QuickFIXn/Transport/StreamFactory.cs

@@ -14,12 +14,12 @@ namespace QuickFix.Transport
     /// </summary>
     internal static class StreamFactory
     {
-        private static Socket? CreateTunnelThruProxy(string destIp, int destPort)
+        private static Socket? CreateTunnelThruProxy(string destIp, int destPort, string destHostName)
         {
             string destUriWithPort = $"{destIp}:{destPort}";
             UriBuilder uriBuilder = new UriBuilder(destUriWithPort);
             Uri destUri = uriBuilder.Uri;
-            IWebProxy webProxy = WebRequest.GetSystemWebProxy();
+            IWebProxy webProxy = WebRequest.DefaultWebProxy ?? WebRequest.GetSystemWebProxy();
 
             try
             {
@@ -44,7 +44,7 @@ internal static class StreamFactory
             Socket socketThruProxy = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
             socketThruProxy.Connect(proxyEndPoint);
 
-            string proxyMsg = $"CONNECT {destIp}:{destPort} HTTP/1.1 \n\n";
+            string proxyMsg = $"CONNECT {destHostName}:{destPort} HTTP/1.1\nHost: {destHostName}:{destPort}\n\n";
             byte[] buffer = Encoding.ASCII.GetBytes(proxyMsg);
             byte[] buffer12 = new byte[500];
             socketThruProxy.Send(buffer, buffer.Length, 0);
@@ -73,7 +73,7 @@ internal static Stream CreateClientStream(IPEndPoint endpoint, SocketSettings se
             if (!settings.SocketIgnoreProxy)
             {
                 // If system has configured a proxy for this config, use it.
-                socket = CreateTunnelThruProxy(endpoint.Address.ToString(), endpoint.Port);
+                socket = CreateTunnelThruProxy(endpoint.Address.ToString(), endpoint.Port, settings.ServerCommonName);
             }
 
             // No proxy.  Set up a regular socket.

RELEASE_NOTES.md

@@ -50,6 +50,7 @@ What's New
 * #516 - remove ability to toggle Session-enable via HttpServer because it never really worked (gbirchmeier)
 * #913/#741 - new FieldMap.ReadGroups for iterating on groups (NoviProg/gbirchmeier)
 * #914 - Optimize MessageCracker.IsHandlerMethod (vasily-balansea)
+* #742 - Improvements to HTTP web proxy  (IanLeeClaxton)
 
 ### v1.12.0