Python OpenCV webcam send image frame over socket

client.py

import cv2
import io
import socket
import struct
import time
import pickle
import zlib

client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(('192.168.1.124', 8485))
connection = client_socket.makefile('wb')

cam = cv2.VideoCapture(0)

cam.set(3, 320);
cam.set(4, 240);

img_counter = 0

encode_param = [int(cv2.IMWRITE_JPEG_QUALITY), 90]

while True:
    ret, frame = cam.read()
    result, frame = cv2.imencode('.jpg', frame, encode_param)
#    data = zlib.compress(pickle.dumps(frame, 0))
    data = pickle.dumps(frame, 0)
    size = len(data)


    print("{}: {}".format(img_counter, size))
    client_socket.sendall(struct.pack(">L", size) + data)
    img_counter += 1

cam.release()

server.py

import socket
import sys
import cv2
import pickle
import numpy as np
import struct ## new
import zlib

HOST=''
PORT=8485

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
print('Socket created')

s.bind((HOST,PORT))
print('Socket bind complete')
s.listen(10)
print('Socket now listening')

conn,addr=s.accept()

data = b""
payload_size = struct.calcsize(">L")
print("payload_size: {}".format(payload_size))
while True:
    while len(data) < payload_size:
        print("Recv: {}".format(len(data)))
        data += conn.recv(4096)

    print("Done Recv: {}".format(len(data)))
    packed_msg_size = data[:payload_size]
    data = data[payload_size:]
    msg_size = struct.unpack(">L", packed_msg_size)[0]
    print("msg_size: {}".format(msg_size))
    while len(data) < msg_size:
        data += conn.recv(4096)
    frame_data = data[:msg_size]
    data = data[msg_size:]

    frame=pickle.loads(frame_data, fix_imports=True, encoding="bytes")
    frame = cv2.imdecode(frame, cv2.IMREAD_COLOR)
    cv2.imshow('ImageWindow',frame)
    cv2.waitKey(1)

First Thank you for the great code,

Can you explain more what this code does? struct.pack(">L", size)
And why you chose ">L".
From here, you can see that regardless the format entered in the struct pack method, when using upack they return the same result.

What is the purpose of arranging the bytes like that?

Yes, Could you possibly explain this?

The full documentation for the "struct.pack(">L", size)" clause can be found right here: https://docs.python.org/3/library/struct.html

thanks a lot it.It's working.

It still work for me, thanks your update

It works for me, but the speed is slow, anyone has suggestions?

Amazing code and really helpfull. It makes so much difference when learning if you can start from code that is functional!

Thanks. :)

Hello, the Server side code gives an syntax error on line 34 over Jetson Nano. But on my Windows PC run very well. What is the difference, Do you have an idea. both system use Python 3.7.

Thanks in advance

Hey did you figure anything out for this? Im trying to do the same.

This is working, while chat gpt didn't the job.
So, good job ;)