ComancheProxy

ComancheProxy is a Man-in-the-Middle (MitM) bridge for MSFS SimConnect, implemented as a bidirectional TCP relay. It forwards SimConnect binary packets while providing real-time patching for specific aircraft profiles, specifically the A2A Comanche.

Installation

• Unpack the release archive to a location of your choosing
• Make sure you have the binary (ComancheProxy.exe) and the config file (config.json) in the same directory

Verification

• Run MSFS and CLS2Sim: CLS2Sim should continue to connect to the simulator as before, but it should say "Connected to Microsoft Flight Simulator X" now.
• Run ComancheProxy.exe, you should see a terminal window with status messages.
• Force a reconnect of CLS2Sim, for example by restarting the program or by starting the Profile Manager (you can use Cancel immediately to close the Profile Manager window).
• When CLS2Sim connects to ComancheProxy, you should see messages in the ComancheProxy window.
• Load the A2A Comanche in MSFS. You should see a message in the ComancheProxy window indicating that the A2A Comanche has been detected.

Usage

• You should be able to start ComancheProxy, CLS2Sim, and MSFS in any order.
• If you start CLS2Sim before ComancheProxy, you will have to force a reconnect (see above).
• If you start ComancheProxy first (recommended), it should automatically connect to MSFS when it starts, and CLS2Sim should automatically connect to ComancheProxy.
• FSEconomy: configure the FSEconomy SimConnect client to use port 5002 (different port!) on 127.0.0.1. Start MSFS and ComancheProxy first, then start the FSE client.

Configuration:

• config.json is configured to handle the A2A Comanche for CLS2Sim and to "convert" the AeroElvira Optica (the one that comes with MSFS) into a C172 for FSEconomy.
• If you don't use one or the other, just ignore the config entries (or remove them, up to you).
• By default, ComancheProxy listens on port 15050 for CLS2Sim connections. CLS2Sim configures this port in its simconnect.cfg for its own use (I assume) and we piggyback on that.
• By default, ComancheProxy listens on port 5002 for FSEconomy connections, for purely historical reasons.
• By default, ComancheProxy tries to connect to MSFS on port 500. By default, MSFS tries to open several SimConnect ports, configured in SimConnect.xml in the MSFS installation directory (at least for the Steam version, not sure about its location in the MS Store version). The ports we care about are "Static IPv4 port" and "Dynamic IPv4 port". If MSFS can't bind to the Static IPv4 port (default: 500), for SOME reason, we have to fall back to the dynamic port, which is not ideal, for OTHER reasons.
• If you notice that ComancheProxy doesn't use the configured port (500) for its connection to MSFS, pick another port that's likely to be unused (e.g. 4711, 5000 or 15000, best below 40000, for reasons), and changing both MSFSPort in config.json and Static IPv4 port in SimConnect.xml to that number.
• If the configured port is not available, ComancheProxy will try to detect the dynamic port. This relies on the correct MSFSProcessName being configured (by default, "FlightSimulator2024"). It's barely tested, only tested on SU5, and it might be brittle. It also appears to have side-effects (it can sometimes trigger the "Safe mode" dialog in the next sim session, even though there was no crash). So a properly configured static port is definitely the better way.

Architecture

The proxy operates between a SimConnect client (such as CLS2Sim) and the MSFS SimConnect server. It executes two asynchronous pump loops to handle upstream (client-facing) and downstream (sim-facing) traffic.

Technical Implementation

Binary Redirection

When the A2A Comanche is detected, the proxy enters redirection mode. It injects sidecar AddToDataDefinition + RequestDataOnSimObject packets directly into the MSFS TCP stream to subscribe to A2A L-Vars, while intercepting the client's own packets to map variable offsets. Incoming RECV_SIMOBJECT_DATA responses are patched in-flight, replacing standard simulator variables with high-fidelity L-Var values from the sidecar subscription.

Performance Optimizations

• Zero-Allocation Parsing: Utilizes Span<byte> and ReadOnlySpan<byte> for packet inspection and manipulation.
• Robust Framing: Employs System.IO.Pipelines for high-performance TCP stream framing, ensuring correct handling of fragmented packets.
• Low Latency: Optimized for high-frequency force-feedback applications where garbage collection pauses must be minimized.
• NativeAOT Compatibility: Compiled with PublishAot=true, avoiding reflection and dynamic code generation.

Development

Prerequisites

• .NET 10.0 SDK
• MSFS SDK (for SimConnect headers/definitions)

Build Commands

The project includes a Makefile for common development tasks:

make build    # build the project
make run      # execute in normal mode
make debug    # execute with verbose logging
make clean    # clean build artifacts

Internal Components

• ProxyBridge: Core bidirectional relay logic.
• SimConnectFramer: Binary framing reactor using PipeReader.
• StateTracker: Thread-safe management of definition mappings and aircraft state.
• TransformationEngine: In-place buffer manipulation for variable patching.