Jetbridge is a simple WebAssembly (WASM) module that allows out-of-process SimConnect modules to act as if they were in-process ones. Specifically, the current development version allows for external modules to dispatch execute_calculator_code calls which can be used to write L: simvars, or even dispatch H: events. Reading the value of local named variables using get_named_variable is also supported.

How does this even work?

Jetbridge establishes a communication protocol using SimConnect's Client Data Areas. It then defines some basic operations that external clients can use, such as calling execute_calculator_code. Jetbridge ships with a C++ SDK which defines a Client class which allows the consumer to communcate with Jetbridge without having to implement the underlying protocol. SDK's for other language may eventually be provided (e.g. C#).

M’kay… But will anyone actually use this?

Jetbridge is currently being used by myself, as well as other FlyByWire Simulations developers, to code hardware drivers for the A32NX. It allows for external programs (such as a hardware driver) to access the inner workings of MSFS in ways not otherwise possible through pure SimConnect.

What are all these folders?

Currently, the repo is structured as a single Visual Studio solution, with 4 projects. The Protocol project is a C++ static library that defines core protocol entities (e.g. Packet). The Module project is the core WASM module and it depends on Protocol. The Client project is another C++ static library that defines the consumer-facing SDK (i.e. the Client) - it also depends on Protocol. Finally, the Example project is a simple C++ command line interface executable that shows how Jetbridge can be used by other developers - it of course depends on Client, and requires Module to be loaded in the simulator.

Client/
├─ Client.vcxproj
Example/
├─ Example.vcxproj
Module/
├─ Module.vcxproj
Protocol/
├─ Protocol.vcxproj
jetbridge.sln

How to use the example

You must first install the Module wasm artifact. You'll have to create a Microsoft Flight Simulator package to do this. If this has been done correctly, you should be able to see an initialising message in the MSFS console. Then, simply start the Example.exe artifact. You can then use the CLI to send Reverse Polish Notation code which will be executed using execute_calculator_code. This should look something like this:

Specifically, use the exe verb followed by the your RNN code. You may also use the get verb followed by the name of a local variable (without the L:) to get the value of an LocalVar. See the example source code for more info

How to use the C++ Client software development kit

Make sure you've correctly imported the static library (header files need to be accessible, .lib file needs to be available to the Linker). Create a Client instance by passing a SimConnect HANDLE:

client = new jetbridge::Client(simconnect);

Then you can send some data using Client->Request:

auto response = client->Request((char*)"x2 (>L:A320_Neo_MFD_NAV_MODE_1)");

This example RPN will set (x opchar) the A320_Neo_MFD_NAV_MODE_1 LocalVar to 2. Client->Request blocks until a response from Jetbridge has been received, or the timeout is reached. If a response is received, it will return a Packet pointer. Important: don't forget to delete this when done using it to avoid a memory leak.

delete response;

Important: You should call the client->HandleReceivedClientDataEvent function with received data for all SIMCONNECT_RECV_ID_CLIENT_DATA events where the RequestID matches jetbridge::kDownlinkRequest. Basically, add something along these lines to your MyDispatchProc:

case SIMCONNECT_RECV_ID_CLIENT_DATA:
  auto e = static_cast<SIMCONNECT_RECV_CLIENT_DATA*>(pData);
  if (e->dwRequestID == jetbridge::kDownlinkRequest) client->HandleReceivedClientDataEvent(e);
  break;

There are also two helper methods to send packets to (1) ExecuteCalculatorCode, and (2) GetNamedVariable:

// Execute the given RPN code:
client->ExecuteCalculatorCode("2 (>L:A320_Neo_MFD_NAV_MODE_1)");
// Get the value of a local named variable:
double value = client->GetNamedVariable("A320_Neo_MFD_NAV_MODE_1");

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Jetbridge is currently at a very early stage of development so bear with us whilst we get everything sorted 🧸