Initial commit: Ananta CBT 4229938 private server with all fixes

Ananta.Server/Ananta.Network/Ananta.Network.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\Ananta.SDK\Ananta.SDK.csproj" />
+  </ItemGroup>
+</Project>

Ananta.Server/Ananta.Network/AssemblyInfo.cs

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+using System.Runtime.CompilerServices;
+[assembly: InternalsVisibleTo("Ananta.App")]

Ananta.Server/Ananta.Network/RpcFrameDispatcher.cs

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+using System.Buffers.Binary;
+using Ananta.SDK.Network;
+using Ananta.SDK.Logging;
+using Ananta.SDK.Rpc;
+
+namespace Ananta.Server.Network;
+
+/// <summary>Decodes the small outer RPC frame envelope shared by login, gate and game sockets.</summary>
+internal static class RpcFrameDispatcher
+{
+    internal static async Task DispatchAsync(
+        RpcRouter router,
+        TcpSession session,
+        Frame frame,
+        CancellationToken cancellationToken)
+    {
+        // Heartbeat request -> heartbeat reply.
+        if (frame.Mode == 0x04)
+        {
+            var heartbeat = frame.Payload.Length == 8 ? frame.Payload : new byte[8];
+            await session.SendFrameAsync(0x03, heartbeat, cancellationToken);
+            return;
+        }
+
+        if (frame.Mode == 0x03 && frame.Payload.Length == 8)
+            return;
+
+        // Client received an invoke that it does not implement. Acknowledge it instead of
+        // letting an optional compatibility RPC break the whole session.
+        if (frame.Mode == 0x08 && frame.Payload.Length >= 9)
+        {
+            RuntimeLogs.RawFrame(session.Log.Scope, "C2S", frame.Mode, frame.Payload, "CLIENT_UNIMPLEMENTED_INVOKE");
+            var methodId = BinaryPrimitives.ReadUInt32LittleEndian(frame.Payload.AsSpan(1, 4));
+            var invokeId = BinaryPrimitives.ReadInt32LittleEndian(frame.Payload.AsSpan(5, 4));
+            await session.ReturnAsync(methodId, invokeId, 0, Array.Empty<byte>(), cancellationToken);
+            return;
+        }
+
+        if (frame.Mode == 0x09)
+        {
+            await router.DispatchAsync(session, frame, cancellationToken);
+            return;
+        }
+
+        RuntimeLogs.RawFrame(session.Log.Scope, "C2S", frame.Mode, frame.Payload, "IGNORED_FRAME_MODE");
+        session.Log.Warn($"ignored frame mode={frame.Mode} payload={frame.Payload.Length}");
+    }
+}