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)

Hi! I have a question. I want to save the frame to video in server. I use VideoWirter, but it dosen't work. Do you know how to save video?

Hi @Syeong2,
You probably already found a solution, but if you are using VideoWriter you MUST make sure that the resolution you set is actually the resolution of the frames you're trying to save. VideoWriter fails silently otherwise and just makes an unplayable ~4kb video file with no actual content. I eventually figured that out a while ago after bashing my head into a table for a couple days...

Hi all, Can you tell me what all the code level modifications that i have to do for sending a image file from server to client. Please help me.

@ajith , Nothing. It just works as it is. Just run the server from command prompt.

if u just stop after the first iteration, u get one single image

Thanks, got it... It's working.

Do you have an idea how the server can recover when client close connection? When I close the client and try to reconnect the server just doesn't seem to want to reconnect.

@CodeAndChoke, if u r using python, plase use Try & Except method. Make sure the except section, again tries to reconnect to the server. Because client has to repeat the "socket.connection" once it is disconnected from server.
Hopes the below script skelton might help u. Please correct me if am wrong.
eg:
#begining script

client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect((HOST, PORT))
while:
try:
# what ever u need to send
except:
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect((HOST, PORT))

Thanks so much! You are the one that I've been searching for a long time!

If there is only one computer. Change the IP to 'localhost'. It works. Thank you for the code!

thank you

Hi! I am a penetration tester. And I want that the Webcam Windows shouldnt open on windows machine. Instead I want the live feed on Kali Linux Machine. What Changes could be made

thank you for your code but i have a problem:
opencv error: unknown error code -10 (Raw image encoder error: empty JPEG image (DNL not supported)) in throwOnError
can you explain

Maybe it's because the cv2 module is not installed properly, maybe the webcam port is busy, maybe the webcam driver is not installed.

Did you run the server first and then the client? Did you run with Linux?

In Linux, you need to install the required modules with the pip command, and run pycharm or any other ide , first run the server and run then the client.
It reads information from the client webcam and it displayed in server program

Thanks 👍 This code is working well. Using this code , How many frames we can send per second ? My requirment is to send 28 frames per second. The server code will be deployed in AWS ec2 instance and the client will be my laptop.

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

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 ;)