#Coding4Fun – How to control your #drone with 20 lines of code! (3/N)

Hi!

Today I’ll write the equivalent of a Hello World in the drone ecosystem. This is a very complex app which:

• take off the drone
• wait a couple of seconds
• lands the drone

I’ve followed the Python code sample from the SDK and the final code is very complex (see below). And it deserves some remarks

• Line 11. The function recv() run in a separated thread to receive messages from the drone. The thread is started on line 44
• Line 19. The function sendMessage() sends messages to the drone. Important, the messages must be UTF-8 encoded. This took me some time, until I figure it out. This time implements a timeout with 5 second until the response is processed in a separated thread
• Lines 31-41. Connection information and sockets to communicate with the drone
• Line 48. Main code for the app. Start the SDK mode, Wait 5 seconds, send the take off message, and then send the land message. A very simple exception catch is implemented here.

Important: When using the SDK, the 1st command should be “command”, as I did in line 49.

Here is the code:

	# Bruno Capuano
	# Simple drone demo
	# connect to drone
	# send take off, sleep and land
	import threading
	import socket
	import sys
	import time
	def recv():
	global response
	while True:
	try:
	response, _ = clientSocket.recvfrom(1024)
	except:
	break
	def sendMessage(command):
	global response
	timestamp = int(time.time() * 1000)
	clientSocket.sendto(command.encode('utf-8'), address)
	while response is None:
	if (time.time() * 1000) – timestamp > 5 * 1000:
	return False
	return response
	# connection info
	UDP_IP = '192.168.10.1'
	UDP_PORT = 8889
	last_received_command = time.time()
	STATE_UDP_PORT = 8890
	address = (UDP_IP, UDP_PORT)
	response = None
	clientSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
	clientSocket.bind(('', UDP_PORT))
	# start threads
	recThread = threading.Thread(target=recv)
	recThread.daemon = True
	recThread.start()
	try:
	msg = "command"
	sendMessage(msg) # start SDK mode
	time.sleep(5)
	msg = "takeoff"
	sendMessage(msg) # takeoff
	time.sleep(3)
	msg = "land"
	sendMessage(msg) # land
	except Exception as e:
	print (f'\nError processing the message:{msg}\n{e}')
	finally:
	print ('\n And now Stop\n')
	sock.close()

view raw DjiTelloHelloWorldSample.py hosted with ❤ by GitHub

Here is the app running at 3X speed so you don’t spend all day watching boring drones videos: