Simple javascript - python rpc via websocket

client.js

class RemoteService {
  #id = 0;
  #socket = null;
  #queue = new Map();

  constructor(wsUrl) {
    this.#socket = new WebSocket(wsUrl);
    this.#socket.addEventListener('error', error => console.log('socket error: ', error));
    this.#socket.addEventListener('message', this._onMessage.bind(this));
    return new Promise((resolve, reject) => {
      this.#socket.addEventListener('open', () => {
        this._onOpen(resolve);
      });
    });
  }

  _send(msg) {
    msg.id = ++this.#id;
    if (this.#id === 2147483647) {
      this.#id = 0;
    }
    this.#socket.send(JSON.stringify(msg));
    return new Promise((resolve, reject) => {
      this.#queue.set(msg.id, [msg.cmd, resolve, reject]);
    });
  }

  async _onOpen(callback) {
    const names = await this._send({cmd: 'list'});
    const send = this._send.bind(this);
    for (const name of names) {
      this[name] = new Proxy({}, {
        get(target, prop, receiver) {
          return (...args) => send({cmd: 'call', name, prop, args});
        }
      });
    }
    callback(this);
  }

  _onMessage(event) {
    const data = JSON.parse(event.data);
    const [cmd, resolve, reject] = this.#queue.get(data.id);
    this.#queue.delete(data.id);
    if (!data.err) {
      resolve(data.data);
    } else {
      reject('remote exception: ' + data.err);
    }
  }
}

(async function() {
  const remote = await new RemoteService('ws://127.0.0.1:3021');
  console.log(await remote.test.hello('world'));
})();

server.py

import asyncio
import traceback

from websockets.server import serve
from yapic import json


class Test:
    def hello(self, text):
        return f'hello {text}'


services = {
    'test': Test(),
}


async def handler(socket):
    async for message in socket:
        msg = json.loads(message)
        err = None
        match msg['cmd']:
            case 'list':
                data = list(services.keys())
            case 'call':
                try:
                    data = getattr(services[msg['name']], msg['prop'])(*msg['args'])
                except Exception as _err:
                    print(traceback.format_exc())
                    err = str(_err)
        await socket.send(json.dumps({
            'id': msg['id'],
            'err': err,
            'data': data,
        }))


async def main():
    async with serve(handler, '127.0.0.1', 3021):
        await asyncio.Future()


asyncio.run(main())