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I want to write a simple TCP server using sockets in Python. The server should send the image to the connected client. The client should receive the image. But, for now on, the client receives only the portion of the image, and I can't even open it.
Server is multi-client using select, but its not the problem here. I think that the problem is with sending image.
I wanted "the protocol" to be very simple here.
SERVER CLIENT
GET
<----------------
IMAGE
----------------->
END OF COMMUNICATION
So the client can only send the "GET" message to server, and the server, after getting the "GET" string, should immediately send the whole image to client. That's it, communication is over.
server.py
#!/usr/bin/env python
import random
import socket, select
from time import gmtime, strftime
image = 'image.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)
bytes = open(image).read()
if data:
sock.send(bytes)
except:
sock.close()
connected_clients_sockets.remove(sock)
continue
server_socket.close()
client.py
#!/usr/bin/env python
import socket
import sys
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:
sock.sendall("GET")
while True:
myfile = open('imagefromserv.png', 'w')
while True:
data = sock.recv(4096)
if not data:
break
myfile.write(data)
myfile.close()
finally:
sock.close()
I'm using Python 2.7 on newest Ubuntu.
------------------------------------------------------------------------------------------------------------------------------------ EDIT ------------------------------------------------------------------------------------------------------------------------------------
Following advices given by one of the users in comments, I TRIED to implement a simple protocol:
CLIENT SERVER
GET\r\n
----------------------------------->
OK\r\n
<-----------------------------------
GET_SIZE\r\n
----------------------------------->
SIZE 1024\r\n
<-----------------------------------
GET_IMG\r\n
----------------------------------->
IMG_DATA\r\r
<-----------------------------------
Everything seems to work, but after the image transfer, my CPU is 100% busy, as top says. And ....
Server's output:
--GET--
--GET_SIZE--
--24518--
--GET_IMG--
Client's output:
--OK--
--SIZE 24518--
--24518--
4096
8192
12288
16384
20480
24523
Image received successfully
Indicates that the client received the image successfully. Is it ok now? I mean, I got the image from server, but I do not know, if I implemented the protocol correctly. Maybe something can be improved here?
client.py:
#!/usr/bin/env python
import socket
import sys
HOST = '127.0.0.1'
PORT = 6666
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = (HOST, PORT)
sock.connect(server_address)
fname = 'fromserver.png'
try:
sock.sendall("GET\r\n")
data = sock.recv(4096)
if data:
txt = data.strip()
print '--%s--' % txt
if txt == 'OK':
sock.sendall("GET_SIZE\r\n")
data = sock.recv(4096)
if data:
txt = data.strip()
print '--%s--' % txt
if txt.startswith('SIZE'):
tmp = txt.split()
size = int(tmp[1])
print '--%s--' % size
sock.sendall("GET_IMG\r\n")
myfile = open(fname, 'wb')
amount_received = 0
while amount_received < size:
data = sock.recv(4096)
if not data :
break
amount_received += len(data)
print amount_received
txt = data.strip('\r\n')
if 'EOF' in str(txt) :
print 'Image received successfully'
myfile.write(data)
myfile.close()
else :
myfile.write(data)
finally:
sock.close()
server.py:
#!/usr/bin/env python
import random
import socket, select
from time import gmtime, strftime
image = 'tux.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)
if data :
txt = data.strip()
print '--%s--'%txt
if txt == 'GET' :
sock.sendall('OK\r\n')
elif txt == 'GET_SIZE' :
with open ('tux.png','rb') as f1:
file_size = len(f1.read())
f1.seek(0)
print '--%s--'%file_size
file_size = '%s' % file_size
sock.sendall('SIZE %s\r\n' % file_size)
elif txt == 'GET_IMG' :
with open(image, 'rb') as fp:
image_data = fp.read()
msg = '%sEOF\r\r' % image_data
sock.sendall(msg)
print msg
except:
sock.close()
connected_clients_sockets.remove(sock)
continue
server_socket.close()
Or maybe I should rather do:
sock.sendall(image_data)
sock.sendall('EOF\r\n')
instead of:
msg = '%sEOF\r\n' % image_data
sock.sendall(msg)
in client?
923
You accidentally forgot to just use HTTP and Twisted.
Server:
from twisted.web.static import File
from twisted.web.resource import Resource
def resource():
resource = Resource()
resource.putChild(b"", File(u"xkcd/sandwich.png"))
return resource
Client:
from filepath import FilePath
from twisted.internet.task import react
from treq import get, content
def main(reactor):
d = get(b"http://localhost:8080/")
d.addCallback(content)
d.addCallback(FilePath(u"image.png").setContent)
return d
react(main, [])
Server demo:
(everything) exarkun@baryon:/tmp/demo$ twist web --class server.resource
2017-02-23T21:32:14-0500 [-] Site starting on 8080
2017-02-23T21:32:14-0500 [twisted.web.server.Site#info] Starting factory <twisted.web.server.Site instance at 0x7fd1ef81a8c0>
2017-02-23T21:32:14-0500 [twisted.application.runner._runner.Runner#info] Starting reactor...
2017-02-23T21:33:01-0500 [twisted.python.log#info] "127.0.0.1" - - [24/Feb/2017:02:33:01 +0000] "GET / HTTP/1.1" 200 21489 "-" "-"
^C
2017-02-23T21:33:05-0500 [-] Received SIGINT, shutting down.
2017-02-23T21:33:05-0500 [-] (TCP Port 8080 Closed)
2017-02-23T21:33:05-0500 [twisted.web.server.Site#info] Stopping factory <twisted.web.server.Site instance at 0x7fd1ef81a8c0>
2017-02-23T21:33:05-0500 [-] Main loop terminated.
(everything) exarkun@baryon:/tmp/demo$
Client demo:
(everything) exarkun@baryon:/tmp/demo$ ls -l image.png
ls: cannot access 'image.png': No such file or directory
(everything) exarkun@baryon:/tmp/demo$ python client.py
(everything) exarkun@baryon:/tmp/demo$ ls -l image.png
-rwxr-xr-x 1 exarkun exarkun 21489 Feb 23 21:33 image.png
(everything) exarkun@baryon:/tmp/demo$
If you want to learn more about how select-loop driven networking is done, you can peruse the Twisted implementation.
119
Your client sends the string "GET". You only want to send and receive image data and "GET" is not image data.
You may have other bugs, it's hard to tell without understanding your protocol. For example, how does one side know what it has gotten all the image data?
34
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