RoboRally/remote_control/robot.py

import socket
import threading
import json


class Robot:
    def __init__(self, marker_id, ip, measurement_server=('127.0.0.1', 42424)):
        self.id = marker_id

        self.t_last_measurement = None
        self.x = None
        self.y = None
        self.angle = None

        self.ip = ip
        self.port = 1234
        self.socket = socket.socket()

        # currently active control
        self.u1 = 0.0
        self.u2 = 0.0

        self.connected = False

        self.measurement_server = measurement_server
        self.measurement_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  # TCP socket
        self.measurement_thread = threading.Thread(target=self.receive_measurements)
        self.measurement_thread.daemon = True # mark thread as daemon -> it terminates automatically when program shuts down
        self.receiving = False


    def connect(self):
        # connect to robot
        try:
            print(f"connecting to robot {self.ip} at {self.ip}:{self.port} ...")
            self.socket.connect((self.ip, self.port))  # connect to robot
            print("connected!")
            self.connected = True
        except socket.error:
            print(f"error: could not connect to robot {self.id} at {self.ip}:{self.port}")

        # connect to measurement server
        print(f"connecting to measurement server on {self.measurement_server} ...")

        try:
            self.measurement_socket.connect(self.measurement_server)
            self.measurement_socket.sendall(f"{self.id}\n".encode())

            self.measurement_socket.settimeout(0.1)
            # check if we receive data from the measurement server
            response = self.measurement_socket.recv(1024)
            if not 'error' in str(response):
                print("... connected! -> start listening for measurements")
                self.measurement_socket.settimeout(None)
                # if so we start the measurement thread
                self.measurement_thread.start()
            else:
                print(f"error: cannot communicate with the measurement server.\n       The response was: {response}")
        except socket.timeout:
            print(f"error: the measurement server did not respond with data.")
        except ConnectionRefusedError:
            print(f"error: could not connect to measurement server at {self.measurement_server}.")

    def send_cmd(self, u1=0.0, u2=0.0):
        if self.socket and self.connected:
            try:
                self.socket.send(f'({u1},{u2})\n'.encode())
            except BrokenPipeError:
                print(f"error: connection to robot {self.id} with ip {self.ip} lost")
                pass
            except ConnectionResetError:
                print(f"error: connection to robot {self.id} with ip {self.ip} lost")
                pass
        else:
            print(f"error: robot {self.id} is not connected to {self.ip}")

    def receive_measurements(self):
        self.receiving = True
        while self.receiving:
            received = str(self.measurement_socket.recv(1024), "utf-8")
            if len(received) > 0:
                last_received = received.split('\n')[-2]
                measurement = json.loads(last_received)
                self.t_last_measurement = measurement['t']
                self.x = measurement['x']
                self.y = measurement['y']
                self.angle = measurement['angle']
            else:
                self.receiving = False
                print(f"measurement server stopped sending data for robot {self.id}")

    def stop_measurement_thread(self):
        self.receiving = False
        self.measurement_thread.join()

    def get_measurement(self):
        return (self.t_last_measurement, self.x, self.y, self.angle)

    def __str__(self):
        connection_state = '' if self.connected else 'not'
        state = self.get_measurement()
        last_measurement = f'last measurement = {state}' if not None in state else 'no measurements available'
        return f"Robot {self.id}: ip = {self.ip}:{self.port} ({connection_state} connected) " + last_measurement

    def __repr__(self):
        return str(self)


class ControlledRobot(Robot):
    def __init__(self, marker_id, ip):
        super().__init__(marker_id, ip)
        self.controller = None

    def start_control(self):
        if self.controller is not None:
            self.controller.start()
        else:
            raise Exception("Error: Cannot start control: there is not controller attached to the robot!")

    def stop_control(self):
        if self.controller is not None:
            self.controller.stop()
        else:
            raise Exception("Error: Cannot stop control: there is not controller attached to the robot!")

    def attach_controller(self, controller):
        self.controller = controller
        self.controller.attach_robot(self)

    def move_to_pos(self, target_pos):
        if self.controller is not None:
            self.controller.set_target_position(target_pos)
        else:
            raise Exception("Error: Cannot move to position: there is not controller attached to the robot!")