Sending image over sockets (ONLY) in Python, image can not be open

Question

I want to upload the image from client to server using ONLY sockets in Python. I designed a very simple protocol flow of how I would like to do this:

CLIENT                                       SERVER
               SIZE 512 (send image size)
         ---------------------------------->
                      GOT SIZE   
         <---------------------------------- 
                 send image itself
         ---------------------------------->
                      GOT IMAGE
         <----------------------------------
                      BYE BYE 
         ---------------------------------->
                server closes socket

Here's my client code:

#!/usr/bin/env python

import random
import socket, select
from time import gmtime, strftime
from random import randint

image = "tux.png"

HOST = '127.0.0.1'
PORT = 6666

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = (HOST, PORT)
sock.connect(server_address)

try:

    # open image
    myfile = open(image, 'rb')
    bytes = myfile.read()
    size = len(bytes)

    # send image size to server
    sock.sendall("SIZE %s" % size)
    answer = sock.recv(4096)

    print 'answer = %s' % answer

    # send image to server
    if answer == 'GOT SIZE':
        sock.sendall(bytes)

        # check what server send
        answer = sock.recv(4096)
        print 'answer = %s' % answer

        if answer == 'GOT IMAGE' :
            sock.sendall("BYE BYE ")
            print 'Image successfully send to server'

    myfile.close()

finally:
    sock.close()

And my server, which receives images from clients:

#!/usr/bin/env python

import random
import socket, select
from time import gmtime, strftime
from random import randint

imgcounter = 1
basename = "image%s.png"

HOST = '127.0.0.1'
PORT = 6666

connected_clients_sockets = []

server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_socket.bind((HOST, PORT))
server_socket.listen(10)

connected_clients_sockets.append(server_socket)

while True:

    read_sockets, write_sockets, error_sockets = select.select(connected_clients_sockets, [], [])

    for sock in read_sockets:

        if sock == server_socket:

            sockfd, client_address = server_socket.accept()
            connected_clients_sockets.append(sockfd)

        else:
            try:

                data = sock.recv(4096)
                txt = str(data)

                if txt.startswith('SIZE'):
                    tmp = txt.split()
                    size = int(tmp[1])

                    print 'got size'

                    sock.send("GOT SIZE")

                elif txt.startswith('BYE'):
                    sock.shutdown()

                elif data:

                    myfile = open(basename % imgcounter, 'wb')

                    data = sock.recv(40960000)
                    if not data:
                        myfile.close()
                        break
                    myfile.write(data)
                    myfile.close()

                    sock.send("GOT IMAGE")
                    sock.shutdown()
            except:
                sock.close()
                connected_clients_sockets.remove(sock)
                continue
        imgcounter += 1
server_socket.close()

For the example image:

The client prints out messages, that suggest, that it send the image to server successfully:

answer = GOT SIZE
answer = GOT IMAGE
Image successfully send to server

The image is created at server's side, but I can not open it. And yes, I tried different images. With no success. I can't open them at server's side, even though they are available there.

Thanks to @BorrajaX, I managed to make it work! Thanks! :)

#!/usr/bin/env python

import random
import socket, select
from time import gmtime, strftime
from random import randint

imgcounter = 1
basename = "image%s.png"

HOST = '127.0.0.1'
PORT = 6666

connected_clients_sockets = []

server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_socket.bind((HOST, PORT))
server_socket.listen(10)

connected_clients_sockets.append(server_socket)

while True:

    read_sockets, write_sockets, error_sockets = select.select(connected_clients_sockets, [], [])

    for sock in read_sockets:

        if sock == server_socket:

            sockfd, client_address = server_socket.accept()
            connected_clients_sockets.append(sockfd)

        else:
            try:

                data = sock.recv(4096)
                txt = str(data)

                if data:

                    if data.startswith('SIZE'):
                        tmp = txt.split()
                        size = int(tmp[1])

                        print 'got size'

                        sock.sendall("GOT SIZE")

                    elif data.startswith('BYE'):
                        sock.shutdown()

                    else :

                        myfile = open(basename % imgcounter, 'wb')
                        myfile.write(data)

                        data = sock.recv(40960000)
                        if not data:
                            myfile.close()
                            break
                        myfile.write(data)
                        myfile.close()

                        sock.sendall("GOT IMAGE")
                        sock.shutdown()
            except:
                sock.close()
                connected_clients_sockets.remove(sock)
                continue
        imgcounter += 1
server_socket.close()

Answer 1

Okay your problem is, in the case of actual image received, you are reading the socket two times and ignoring the data in the first read and just writing the data received in the second read. So your image file is incomplete. See my fix below , you can optimize from this taking it as starting point. It works as such.

#!/usr/bin/env python

import random
import socket, select
from time import gmtime, strftime
from random import randint

imgcounter = 1
basename = "image%s.png"

HOST = '127.0.0.1'
PORT = 6666

connected_clients_sockets = []

server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_socket.bind((HOST, PORT))
server_socket.listen(10)

connected_clients_sockets.append(server_socket)
buffer_size = 4096

while True:

    read_sockets, write_sockets, error_sockets = select.select(connected_clients_sockets, [], [])



    for sock in read_sockets:

        if sock == server_socket:

            sockfd, client_address = server_socket.accept()
            connected_clients_sockets.append(sockfd)

        else:
            try:
                print ' Buffer size is %s' % buffer_size
                data = sock.recv(buffer_size)
                txt = str(data)

                if txt.startswith('SIZE'):
                    tmp = txt.split()
                    size = int(tmp[1])

                    print 'got size'
                    print 'size is %s' % size

                    sock.send("GOT SIZE")
                    # Now set the buffer size for the image 
                    buffer_size = 40960000

                elif txt.startswith('BYE'):
                    sock.shutdown()

                elif data:

                    myfile = open(basename % imgcounter, 'wb')

                    # data = sock.recv(buffer_size)
                    if not data:
                        myfile.close()
                        break
                    myfile.write(data)
                    myfile.close()

                    sock.send("GOT IMAGE")
                    buffer_size = 4096
                    sock.shutdown()
            except:
                sock.close()
                connected_clients_sockets.remove(sock)
                continue
        imgcounter += 1
server_socket.close()