Python code for connecting to Udacity Self-Driving Cars Simulator (Tested with term 2 project 5 on model predictive control).

mpc.py

import json
import asyncio
import websockets

def _check_mode(msg):
    return  "Auto" if msg and msg[:2] == '42' else "Manual"

def _parse_telemetry(msg):
    msg_json = msg[2:]
    parsed = json.loads(msg_json)
    
    msg_type = parsed[0]
    assert msg_type == 'telemetry' , "Invalid message type {}".format(msg_type) 
    
    # Telemetry values
    values = parsed[1]
    
    return values
    
    
async def control_loop(websocket, path):
    async for message in websocket:
        if _check_mode(message) is 'Auto':
            telemetry  = _parse_telemetry(message)
            
            psi = telemetry['psi']
            ptsx = telemetry['ptsx']
            ptsy = telemetry['ptsy']
            speed = telemetry['speed']
            steering = telemetry['steering_angle']
            throttle = telemetry['throttle']
            x = telemetry['x']
            y = telemetry['y']
            
            #Implement your model predictive control here.
        else:
            print("Falling back to manual mode")


asyncio.get_event_loop().run_until_complete(
websockets.serve(control_loop, 'localhost', 4567))
asyncio.get_event_loop().run_forever()