Implement handshake Hello NetControlMessage, recv and send

src/Prospect.Unreal/Runtime/UWorld.cs

@@ -1,7 +1,9 @@
 using Prospect.Unreal.Core;
+using Prospect.Unreal.Exceptions;
 using Prospect.Unreal.Net;
 using Prospect.Unreal.Net.Channels;
 using Prospect.Unreal.Net.Packets.Bunch;
+using Prospect.Unreal.Net.Packets.Control;
 using Serilog;
 
 namespace Prospect.Unreal.Runtime;
@@ -60,7 +62,12 @@ public abstract class UWorld : FNetworkNotify, IAsyncDisposable
 
     public bool NotifyAcceptingChannel(UChannel channel)
     {
-        var driver = channel.Connection.Driver!;
+        if (channel.Connection?.Driver == null)
+        {
+            throw new UnrealNetException();
+        }
+        
+        var driver = channel.Connection.Driver;
         if (!driver.IsServer())
         {
             throw new NotSupportedException("Client code");
@@ -81,9 +88,59 @@ public abstract class UWorld : FNetworkNotify, IAsyncDisposable
         }
     }
 
-    public void NotifyControlMessage(UNetConnection connection, byte messageType, FInBunch bunch)
+    public void NotifyControlMessage(UNetConnection connection, NMT messageType, FInBunch bunch)
     {
+        if (NetDriver == null)
+        {
+            throw new UnrealNetException();
+        }
         
+        if (!NetDriver.IsServer())
+        {
+            throw new NotSupportedException("Client code");
+        }
+        else
+        {
+            Logger.Verbose("Level server received: {MessageType}", messageType);
+
+            if (!connection.IsClientMsgTypeValid(messageType))
+            {
+                Logger.Error("IsClientMsgTypeValid FAILED ({MessageType}): Remote Address = {Address}", (int)messageType, connection.LowLevelGetRemoteAddress());
+                bunch.SetError();
+                return;
+            }
+
+            switch (messageType)
+            {
+                case NMT.Hello:
+                {
+                    if (NMT_Hello.Receive(bunch, out var isLittleEndian, out var remoteNetworkVersion, out var encryptionToken))
+                    {
+                        // TODO: Version check.
+
+                        if (string.IsNullOrEmpty(encryptionToken))
+                        {
+                            connection.SendChallengeControlMessage();
+                        }
+                        else
+                        {
+                            throw new NotImplementedException("Encryption");
+                        }
+                    }
+                    break;
+                }
+
+                case NMT.Login:
+                {
+                    throw new NotImplementedException();
+                }
+
+                default:
+                {
+                    throw new NotImplementedException($"Unhandled control message {messageType}");
+                }
+            }
+        }
     }
 
     public async ValueTask DisposeAsync()