To connect to Eachine EX4 using Qgroundcontrol/MAVlink running on a computer, first run this script.

eachine-ex4-bond-ip.py

import socket
from time import sleep

DRONE_IP = '172.50.10.1'
DRONE_BOND_PORT = 4646

RESET_CMD=b'{"CMD":0,"PARAM":-1}\n'
BOND_CMD=b'{"CMD":89,"PARAM":1}\n'

EXPECTED_SERVER_RESPONSE = '{ "CMD": 89, "PARAM": -1, "RESULT": 1 }'

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = (DRONE_IP,DRONE_BOND_PORT)
sock.connect(server_address)

try:
    sock.send(RESET_CMD)
    print('1. Received from server: ', sock.recv(5000).decode())
    sleep(1)
    sock.send(BOND_CMD)
    print('2. Received from server: ', sock.recv(5000).decode())
    sleep(2)
    result = sock.recv(5000).decode()
    print('3. Received from server: ', result)
    if result == EXPECTED_SERVER_RESPONSE:
        print('IP address bond success!')
    else:
        print('IP address bond failed!')
finally:
    print('Closing socket ..')
    sock.close()