Quectel RM520N AT via Ethernet client

at.py

import socket
import struct
import time
import threading

SERVER_IP = "192.168.225.1"
SERVER_PORT = 1555
BUFFER_SIZE = 2048 * 4

def main(argv):
    # payload = 'AT'

    client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    print("Connecting...")
    client_socket.connect((SERVER_IP, SERVER_PORT))
    print("OK")

    def reader():
        while True:
            hdr = client_socket.recv(3)
            if len(hdr) < 3:
                exit()
            command_id, length = struct.unpack('>BH', hdr)
            value = client_socket.recv(length)
            value_str = value.decode('utf-8', errors='ignore')
            print(command_id, value_str)
    t = threading.Thread(target=reader, daemon=True)
    t.start()
    while True:
        payload = input() + "\r\n"
        msg = struct.pack(">BH", 0xA4, len(payload)) + payload.encode()
        client_socket.send(msg)