Networking

Takeaways:

• Native: Arbitrary TCP, UDP connections can be made.
• Native: Can communicate using the WebSocket protocol.
• WASM: Need to obey browser security rules.
• WASM: Can communicate using WebSockets.
• WASM: Receiving messages is done through callbacks, and requires a lot of wiring to pass the message back to Rust.
• Github issue(s): amethyst#2251

Native

Sending Messages

1. 🌐 You want to play online.
2. 🔌 You open a connection.
3. 📡 You send data.

Receiving Messages

1. Check for messages received by the network socket.
2. Iterate and decide what to do with them.

WASM

Note: If you retain the TCP / UDP code, the WASM application doesn't crash, but simply logs that this part is not implemented.

Sending Messages

1. 🌐 You want to play online.

2. 📨 You send the WebSocket and the message byte array (accessed through SharedArrayBuffer) to JS.

   #[wasm_bindgen]
   extern "C" {
       fn web_socket_send(web_socket: &WebSocket, src: &[u8]);
   }
   

3. 📋 You clone the data.

4. 💽 You send data to the web socket.

   function web_socket_send(web_socket, src) {
       // Turn the array view into owned memory.
       var standalone = [...src];
       // Make it a Uint8Array.
       let bytes = new Uint8Array(standalone);
   
       web_socket.send(bytes);
   }
   

5. 📮 The message is sent when the main thread returns.

Receiving Messages

1. When creating the web socket, set up an onmessage callback.
2. In the onmessage callback, use a [FileReader] to begin to read the bytes from the socket.
3. Also, set up an onload callback for when the FileReader has finished reading bytes.
4. In the onload callback, send the message through to Rust using a channel.
5. In Rust, read from the channel for any messages.