I am writhing a python script in order to communicate to my tello drone via wifi. Once connected with the drone I can send UDP packets to send commands (this works perfectly fine). I want to receive the video stream from the drone via UDP packets arriving at my udp server on port 11111. This is described in the SDK documentation, "https://dl-cdn.ryzerobotics.com/downloads/tello/20180910/Tello%20SDK%20Documentation%20EN_1.3.pdf". print ('\r\n\r\nTello drone communication tool\r\n') print("...importing modules...") import threading import socket import sys import time import platform import cv2 print("Modules imported") print("...Initialiasing UDP server to get video stream....") drone_videostream = cv2.VideoCapture('udp://@0.0.0.0:11111') print("Server initialised") # my local adress to receive UDP packets from tello DRONE host = '' port = 9000 locaddr = (host,port) print("...creation of UDP socket...") # Create a UDP socket (UDP Portocol to receive and send UDP packets from/to drone) sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # Got drone port and ip adress from network (explained in official SDK documentation) tello_address = ('192.168.10.1', 8889) print("UDP socket created") sock.bind(locaddr) width = 320 height = 240 def receiveStream() : print("...receiving stream...") while True : ret, frame = drone_videostream.read() img = cv2.resize(frame, (width, height)) cv2.imshow("LiveStream", frame) cv2.waitKey(1) drone_videostream.release() cv2.destroyAllWindows() def receiving(): while True: try: data, server = sock.recvfrom(1518) print(data.decode(encoding="utf-8")) except Exception: print ('\nExit . . .\n') break print ("...initialiazing connection with tello drone...") message = "command" message = message.encode(encoding="utf-8") sent = sock.sendto(message, tello_address) print("Connection established") #create a thread that will excute the receiving() function receiveThread = threading.Thread(target=receiving) receiveThread.start() receiveStreamThread = threading.Thread(target=receiveStream) while True : message = input(str("Enter a command :\r\n")) if message == "streamon" : message = message.encode(encoding="utf-8") sent = sock.sendto(message, tello_address) receiveStreamThread.start() else : message = message.encode(encoding="utf-8") sent = sock.sendto(message, tello_address) When I send the "streamon" command to the drone, I am unable to read the sended UDP packets. I get the following error : error: (-215:Assertion failed) !ssize.empty() in function 'cv::resize' This means that the frames are empty, thus, no image received. Do you know why I dont receive them ? Thank you very much for your help in advance, Best Continue reading...