Add HTTP Server

Ooui/Ooui.csproj

@@ -1,7 +1,8 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>netstandard1.4</TargetFramework>
+    <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
-
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="10.0.2" />
+  </ItemGroup>
 </Project>

Ooui/Server.cs

@@ -0,0 +1,92 @@
+using System;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Net;
+using System.Net.WebSockets;
+
+namespace Ooui
+{
+    public class Server
+    {
+        public Task RunAsync (string listenerPrefix)
+        {
+            return RunAsync (listenerPrefix, CancellationToken.None);
+        }
+
+        public async Task RunAsync (string listenerPrefix, CancellationToken token)
+        {
+            var listener = new HttpListener ();
+            listener.Prefixes.Add (listenerPrefix);
+            listener.Start ();
+            Console.WriteLine ($"Listening at {listenerPrefix}...");
+
+            while (!token.IsCancellationRequested) {
+                var listenerContext = await listener.GetContextAsync ();
+                if (listenerContext.Request.IsWebSocketRequest) {
+                    ProcessWebSocketRequest (listenerContext, token);
+                }
+                else {
+                    listenerContext.Response.StatusCode = 400;
+                    listenerContext.Response.Close ();
+                }
+            }
+        }
+
+        async void ProcessWebSocketRequest (HttpListenerContext listenerContext, CancellationToken token)
+        {
+            WebSocketContext webSocketContext = null;
+            try {
+                webSocketContext = await listenerContext.AcceptWebSocketAsync(subProtocol: null);
+                Console.WriteLine ("Accepted WebSocket: {0}", webSocketContext);
+            }
+            catch (Exception e) {
+                listenerContext.Response.StatusCode = 500;
+                listenerContext.Response.Close();
+                Console.WriteLine ("Failed to accept WebSocket: {0}", e);
+                return;
+            }
+
+            WebSocket webSocket = null;
+
+            try {
+                webSocket = webSocketContext.WebSocket;
+
+                var receiveBuffer = new byte[1024];
+
+                while (webSocket.State == WebSocketState.Open && !token.IsCancellationRequested) {
+                    var receiveResult = await webSocket.ReceiveAsync(new ArraySegment<byte>(receiveBuffer), token);
+
+                    if (receiveResult.MessageType == WebSocketMessageType.Close) {
+                        await webSocket.CloseAsync (WebSocketCloseStatus.NormalClosure, "", token);
+                    }
+                    else if (receiveResult.MessageType == WebSocketMessageType.Binary) {
+                        await webSocket.CloseAsync (WebSocketCloseStatus.InvalidMessageType, "Cannot accept binary frame", token);
+                    }
+                    else {
+                        var size = receiveResult.Count;
+                        while (!receiveResult.EndOfMessage) {
+                            if (size >= receiveBuffer.Length) {
+                                await webSocket.CloseAsync (WebSocketCloseStatus.MessageTooBig, "Message too big", token);
+                                return;
+                            }
+                            receiveResult = await webSocket.ReceiveAsync (new ArraySegment<byte>(receiveBuffer, size, receiveBuffer.Length - size), token);
+                            size += receiveResult.Count;
+                        }
+                        var receivedString = Encoding.UTF8.GetString (receiveBuffer, 0, size);
+                        Console.WriteLine ("RECEIVED: {0}", receivedString);
+
+                        var outputBuffer = new ArraySegment<byte> (Encoding.UTF8.GetBytes ($"You said: {receivedString}"));
+                        await webSocket.SendAsync (outputBuffer, WebSocketMessageType.Text, true, token);
+                    }
+                }
+            }
+            catch (Exception e) {
+                Console.WriteLine ("Exception: {0}", e);
+            }
+            finally {
+                webSocket?.Dispose();
+            }
+        }
+    }
+}