Make Camera Endpoint Compatible with NGROK

Certain ngrok configurations pass an "X-Original-Host" header as part of
the request if the host header is rewritten. This adds support for
detecting and using that header to make the Camera listing endpoint
seamless for clients using an ngrok URL

Telemachus/src/CameraResponsibility.cs

@@ -19,6 +19,7 @@ public class CameraResponsibility : IHTTPRequestResponder
         /// The page prefix that this class handles
         public const String PAGE_PREFIX = "/telemachus/cameras";
         public const String CAMERA_LIST_ENDPOINT = PAGE_PREFIX;
+        public const String NGROK_ORIGINAL_HOST_HEADER = "X-Original-Host";
         protected Regex _cameraNameEndpointRegex;
         protected Regex cameraNameEndpointRegex
         {
@@ -80,7 +81,17 @@ private static IDictionary<string, object> parseJSONBody(string jsonBody)
 
         public string cameraURL(HttpListenerRequest request, CameraCapture camera)
         {
-            return request.Url.Scheme + "://" + request.UserHostName + PAGE_PREFIX + "/" + UnityEngine.WWW.EscapeURL(camera.cameraManagerName());
+            String hostname = "";
+            if (request.Headers.Contains(NGROK_ORIGINAL_HOST_HEADER))
+            {
+                hostname = request.Headers[NGROK_ORIGINAL_HOST_HEADER];
+            }
+            else
+            {
+                hostname = request.UserHostName;
+            }
+
+            return request.Url.Scheme + "://" + hostname + PAGE_PREFIX + "/" + UnityEngine.WWW.EscapeURL(camera.cameraManagerName());
         }
 
         public bool processCameraManagerIndex(HttpListenerRequest request, HttpListenerResponse response)