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Do I need a sleep on receiving data from socket Python

I'm new to sockets. I've written a simple 'proxy' server in Python that will just catch the data from the remote server and send it to my client (browser). I was wondering: is there a way to send the response_text without a time.sleep? While i try to delete time.sleep(0.5) I only get one package of data from the remote server so the 'Content-lenght' isn't equal to the length of the package and I get an error (I'm using recv() to get a buffer with size equaled to buffer_size, so if the server data needs more then one package of 4096 bytes I need to catch it in the next package). With the time.sleep i get all the packages of data from the remote server and I can send the data to my browser. Am I doing something wrong? Or I just don't know enough? Can someone help?
The code:
# coding: utf-8
import socket
import sys
import time
from thread import *
max_conn = 5
buffer_size = 4096
def proxy_server(webserver, port, conn, addr, data):
try:
remote_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
remote_sock.connect((webserver, port))
remote_sock.send(data)
response_text = ''
while True:
time.sleep(0.5)
response = remote_sock.recv(buffer_size)
response_text += response
if len(response) < buffer_size:
remote_sock.close()
break
conn.sendall(response_text)
conn.close()
except socket.error, msg:
print 'Proccessing error. Error Code: ' + str(msg[0]) + ', Wiadomość: ' + msg[1]
remote_sock.close()
conn.close()
sys.exit()
def conn_string(conn, data, address):
header = data.split('\r\n')
method, address, protocol = header[0].split(' ')
host_key, host_value = header[1].split(': ')
proxy_server(host_value, 80, conn, address, data)
def start():
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(('', 8001))
sock.listen(max_conn)
print 'Proxy: on'
except socket.error, msg:
print 'Failed creating a socket. Error Code: ' + str(msg[0]) + ', Wiadomość: ' + msg[1]
sys.exit()
while True:
try:
connection, address = sock.accept()
data = connection.recv(buffer_size)
# start_new_thread(conn_string, (connection, data, address))
conn_string(connection, data, address)
except KeyboardInterrupt:
sock.close()
print "Socket closed"
sys.exit()
if __name__ == "__main__":
start()

Don't use time.sleep() , it makes your proxy very slow , and its not efficient .
You need to set your socket in non-blocking mode , with a timeout .
You can do this with socket.settimeout()
I made a few modifications to your proxy_server , it should be much faster now .
def proxy_server(webserver, port, conn, addr, data):
try:
remote_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
remote_sock.connect((webserver, port))
remote_sock.send(data)
remote_sock.settimeout(0.5)
response_text = ''
while True:
try :
response = remote_sock.recv(buffer_size)
if len(response) == 0:
break
except :
break
response_text += response
conn.sendall(response_text)
except socket.error, msg:
if str(msg) != 'timed out' :
print 'Proccessing error. Error Code: ' + str(msg[0]) + ', Wiadomość: ' + msg[1]
remote_sock.close()
conn.close()
The rest of your code is quite ok , but you may want to use multithreading
if you want to handle multiple clients at the same time .

how to combine server and client to work together as one program?

is their a function that i can check if there is incoming connection or not to the server ( inside While Loop )?
import socket
import sys
HOST = ''
PORT = 8888
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
try:
s.bind((HOST, PORT))
except socket.error , msg:
print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]
sys.exit()
print 'Socket bind complete'
s.listen(10)
print 'Socket now listening'
while 1:
##### IF there is request to server Do #####
conn, addr = s.accept()
print 'Connected with ' + addr[0] + ':' + str(addr[1])
data = conn.recv(1024)
reply = 'OK...' + data
conn.sendall(reply)
##### Else Do something else like print for example #####
print 'Nothing yet'
conn.close()
s.close()
what i want to do is to check if there is no request to my server i will do something else.
is it possible to do that?

Yes, there's a such function.
From man accept:
In order to be notified of incoming connections on a socket, you can
use select(2), poll(2), or epoll(7). A readable event will be
delivered when a new connection is attempted and you may then call
accept() to get a socket for that connection.
In python you can use select combined with the timeout parameter:
import select
# somewhere in a while loop
timeout = 0
incoming_connections, _, __ = select.select([s], [], [], timeout)
if incoming_connections:
conn, addr = s.accept()
...
else:
...

socket is not listening for multiple request

Here is the code for server -
import socket, select,re
def getSocket( idd):
return CONNECTION_LIST[idd]
def broadcast_data (sock, message):
for socket in CONNECTION_LIST:
if socket != server_socket and socket != sock :
try :
socket.send(message)
except :
socket.close()
CONNECTION_LIST.remove(socket)
def single_client (sock , message , idd):
socket = getSocket ( idd )
if socket :
socket.send(message)
else:
print "chudap"
if __name__ == "__main__":
CONNECTION_LIST = []
RECV_BUFFER = 4096
PORT = 5000
PORTC = 2225
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_socket.bind(("0.0.0.0", PORT))
server_socket.listen(10)
listen = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
listen.bind(("0.0.0.0" , PORTC))
#listen.listen(10)
CONNECTION_LIST.append(server_socket)
CONNECTION_LIST.append(listen)
print "Chat server started on port " + str(PORT)
idd = 1
while 1:
# Get the list sockets which are ready to be read through select
read_sockets,write_sockets,error_sockets = select.select(CONNECTION_LIST,[],[])
for sock in read_sockets:
if sock == server_socket:
sockfd, addr = server_socket.accept()
CONNECTION_LIST.append(sockfd)
#name = sockfd.recv(RECV_BUFFER)
print "connected from ip %s, id assigned is %d" % (addr[0] , idd)
broadcast_data(sockfd, "client with IP %s has entered with id = %d\n" % (addr[0] , idd))
idd += 1
elif sock == listen:
print "debugging"
data,addr = listen.recvfrom(RECV_BUFFER)
print "Received server probe request from [%s:%s]"%addr
listen.sendto("iam" , addr)#(addr[0] , 2624))
listen.close()
CONNECTION_LIST.remove(listen)
listen = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
listen.bind(("0.0.0.0" , PORTC))
CONNECTION_LIST.append(listen)
else:
try:
data = sock.recv(RECV_BUFFER)
if re.findall(r'.*/msg\d+' , data):
#print "got single client message request" + data
name = "private message from " + re.findall('([^:]+): /msg(\d+)([^"]+)' , data)[0][0] + ": "
#print name
eid = int(re.findall('([^:]+): /msg(\d+)([^"]+)' , data)[0][1])
#print eid
data = re.findall('([^:]+): /msg(\d+)([^"]+)' , data)[0][2]
#print data
data = name + data
#print "single client message sent with id = %d" %eid
single_client( sock , data , int(eid))
elif data:
broadcast_data(sock, data)
except:
broadcast_data(sock, "Client (%s, %s) is offline" % addr)
print "Client (%s, %s) is offline" % addr
sock.close()
CONNECTION_LIST.remove(sock)
continue
server_socket.close()
Here is the code for client -
import socket, select, string, sys
def prompt() :
sys.stdout.write('<You>: ')
sys.stdout.flush()
def exit(sock):
print "\n Thank you for using chat application\nBye"
sock.close()
sys.exit()
def printUsage():
print "1. By default your message will be sent to all clients sitting on the chat server"
print "2. You can send a private message to a person by starting your message as \"/msg{id}{Your message}\" for example /msg2Hi will send \"hi\" to client with id 2"
print "3. For quitting simply type \"/q\" or \"/quit\""
prompt()
PORTS = 2225
PORTC = 2624
if __name__ == "__main__":
broad = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
broad.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
broad.bind(( '0.0.0.0' , 2624) )
broad.sendto(b'whoisserver', 0, ("255.255.255.255", PORTS))
broad.settimeout(10)
print 15*"-" + "WELCOME TO CHATVILLE" + 15*"-" + "\nFinding the server"
try:
data , addr = broad.recvfrom(10)
except:
print "Can't find server ! Please ensure that server is up"
broad.close()
sys.exit()
broad.close()
if data <> "iam":
print "Can't find a valid server !"
sys.exit()
host = addr[0]
port = 5000
print addr
# host = sys.argv[1]
# port = int(sys.argv[2])
# print host,port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2)
name = raw_input("Please Enter your name: ")
try :
s.connect((host, port))
s.send(name)
except :
print 'Unable to connect'
sys.exit()
print 'Connected to remote host. Enjoy...............................'
name = "<" + name + ">" + ": "
print " - type /h to see usage instructions any time :) - "
prompt()
while 1:
socket_list = [sys.stdin, s]
read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])
for sock in read_sockets:
if sock == s:
data = sock.recv(4096)
if not data :
print '\nDisconnected from chat server'
sys.exit()
else :
print ""
sys.stdout.write(data)
prompt()
else :
msg = sys.stdin.readline()
if str.startswith(msg, "/h") or str.startswith(msg,"/help"):
printUsage()
elif str.startswith(msg, "/quit") or str.startswith(msg,"/q"):
exit(s)
else:
msg = name + msg
s.send(msg)
prompt()
Main problem is that only one client is able to connect as soon as the first client connects are to server no other client is able to discover the server.
I tried by looking at the client's code by tcpdump and I can see the packet going at port number 2225, but the socket listen is not responding at all after the first connection.
PS - earlier I was not making instance of listen socket again and again but I tried this also and it didn't work out.

In the sever broadcast_data() does not exclude the UDP socket (listen) from the sockets to write to, and so it calls send() on that socket. This fails with exception
socket.error: [Errno 89] Destination address required
because no address is supplied (and can't be with socket.send()). The exception handler then closes the UDP socket and no further messages from new clients can be received. That's why additional clients can not connect to the server.
This is a perfect example of why it is not a good idea to use a bare except, i.e. an except statement that handles all exceptions. In this case the handler closes the UDP socket without even logging the fact. There are other instances of bare except statements in your code. I suggest that you handle specific exceptions to avoid this sort of bug. You can fix it by adding the UDP socket to the list of sockets to ignore:
def broadcast_data(sock, message):
for socket in CONNECTION_LIST:
if socket not in (server_socket, sock, listen):
try :
socket.send(message)
except socket.error as exc:
print '!!! An error occurred while writing to client. !!!'
print exc
socket.close()
CONNECTION_LIST.remove(socket)
Now no attempt will be made to send messages to the UDP listen socket, and the socket won't be closed due to error.
P.S. the code in your main loop that closes and reopens the listen socket is not necessary.

reading port number as an argument and do stuff

I wrote the following script in python:
#!/usr/bin/python
import socket
import sys
import os
host=sys.argv[1]
port=sys.argv[2]
if len(sys.argv) != 3:
print 'Usage: python %s <HostName> <PortNumber>' % (sys.argv[0])
sys.exit();
try:
s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except socket.error, msg:
print 'Failed to creat socket. Error code: ' + str(msg[0]) + ' Error message: ' + msg[1]
sys.exit();
try:
host_ip=socket.gethostbyname(host)
except socket.gaierror:
print 'Host name could not be resolved. Exiting...'
sys.exit();
print 'IP address of ' + host + ' is ' + host_ip + ' .'
try:
s.connect((host_ip, port)) #OR s.connect((host_ip, sys.argv[2]))
except socket.error, (value,message):
if s:
s.close();
print 'Socket connection is not established!\t' + message
sys.exit(1);
print 'Socket connected to ' + host + 'on IP ' + host_ip + 'on port number ' + port + '.'
But when I run it this error occures:
s.connect((host_ip, port))
return getattr(self._sock,name)(*args)
TypeError: an integer is required
What is wrong here?
Thanks

The error message is the answer.
port shall be an integer and you are passing in str
before you call s.connect((host_ip, port)) do
port = int(port)

You should use argparse to process your arguments. It provides many useful features in addition to making it easy to fix your immediate problem (not making the port number an integer). Replace
host=sys.argv[1]
port=sys.argv[2]
if len(sys.argv) != 3:
print 'Usage: python %s <HostName> <PortNumber>' % (sys.argv[0])
sys.exit();
with
import argparse
p = argparse.ArgumentParser()
p.add_argument("host")
p.add_argument("port", type=int)
args = p.parse_args()
# And optionally
host = args.host
port = args.port

connect() requires an integer for the port argument, and since you accepted port as an argument it's a string. Make sure you typecast it as an int - s.connect((host_ip, int(port)).

The sys.argv list is a list of strings, so you should convert it to an integer with the build-in int() function:
port = int(sys.argv[2])

Python socket server/client programming

So I am just getting into python and trying out some stuff. To start, I am making a server that does simple stuff like "GET"s stored text, "STORE"s new text over the old stored text, and "TRANSLATE"s lowercase text into uppercase. But I have a few questions. Here is my code so far:
import socket
HOST = '' # Symbolic name meaning the local host
PORT = 24069 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
try:
s.bind((HOST, PORT))
except socket.error , msg:
print 'Bind failed. Error code: ' + str(msg[0]) + 'Error message: ' + msg[1]
sys.exit()
print 'Socket bind complete'
s.listen(1)
print 'Socket now listening'
while 1:
conn, addr = s.accept()
print 'Connected with ' + addr[0] + ':' + str(addr[1])
data = conn.recv(1024)
reply = 'OK...' + data
if not data: break
conn.send(data)
conn.close()
s.close()
To start changing text from a client into uppercase, from my other programming knowledge, I assume I'd store the client's text in a variable and then run a function on it to change it to uppercase. Is there such a function in python? Could someone please give me a snippet of how this would look?
And lastly, how would I do something like a GET or STORE in python? My best guess would be:
data = conn.recv(1024)
if data == GET: print text
if data == STORE: text = data #Not sure how to reference the text that the client has entered
Thank you so much for any help! :)
Note to self:
import socket
HOST = '' # Symbolic name meaning the local host
PORT = 24069 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
try:
s.bind((HOST, PORT))
except socket.error , msg:
print 'Bind failed. Error code: ' + str(msg[0]) + 'Error message: ' + msg[1]
sys.exit()
print 'Socket bind complete'
s.listen(1)
print 'Socket now listening'
# Accept the connection
(conn, addr) = s.accept()
print 'Server: got connection from client ' + addr[0] + ':' + str(addr[1])
storedText = 'Hiya!'
while 1:
data = conn.recv(1024)
tokens = data.split(' ', 1)
command = tokens[0]
if command == 'GET':
print addr[0] + ':' + str(addr[1]) + ' sends GET'
reply = storedText
elif command == 'STORE':
print addr[0] + ':' + str(addr[1]) + ' sends STORE'
storedText = tokens[0]
reply = '200 OK\n' + storedText
elif command == 'TRANSLATE':
print addr[0] + ':' + str(addr[1]) + ' sends TRANSLATE'
storedText = storedText.upper()
reply = storedText
elif command == 'EXIT':
print addr[0] + ':' + str(addr[1]) + ' sends EXIT'
conn.send('200 OK')
break
else:
reply = '400 Command not valid.'
# Send reply
conn.send(reply)
conn.close()
s.close()

I see that you're quite new to Python. You can try to find some code example, and you should also learn how to interpret the error message. The error message will give you the line number where you should look at. You should consider that line or previous line, as the error may be caused by previous mistakes.
Anyway, after your edits, do you still have indentation error?
On your real question, first, the concept.
To run client/server, you'll need two scripts: one as the client and one as the server.
On the server, the script will just need to bind to a socket and listen to that connection, receive data, process the data and then return the result. This is what you've done correctly, except that you just need to process the data before sending response.
For starter, you don't need to include the accept in the while loop, just accept one connection, then stay with it until client closes.
So you might do something like this in the server:
# Accept the connection once (for starter)
(conn, addr) = s.accept()
print 'Connected with ' + addr[0] + ':' + str(addr[1])
stored_data = ''
while True:
# RECEIVE DATA
data = conn.recv(1024)
# PROCESS DATA
tokens = data.split(' ',1) # Split by space at most once
command = tokens[0] # The first token is the command
if command=='GET': # The client requests the data
reply = stored_data # Return the stored data
elif command=='STORE': # The client want to store data
stored_data = tokens[1] # Get the data as second token, save it
reply = 'OK' # Acknowledge that we have stored the data
elif command=='TRANSLATE': # Client wants to translate
stored_data = stored_data.upper() # Convert to upper case
reply = stored_data # Reply with the converted data
elif command=='QUIT': # Client is done
conn.send('Quit') # Acknowledge
break # Quit the loop
else:
reply = 'Unknown command'
# SEND REPLY
conn.send(reply)
conn.close() # When we are out of the loop, we're done, close
and in the client:
import socket
HOST = '' # Symbolic name meaning the local host
PORT = 24069 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST,PORT))
while True:
command = raw_input('Enter your command: ')
if command.split(' ',1)[0]=='STORE':
while True:
additional_text = raw_input()
command = command+'\n'+additional_text
if additional_text=='.':
break
s.send(command)
reply = s.recv(1024)
if reply=='Quit':
break
print reply
Sample run (first run the server, then run the client) on client console:
Enter your command: STORE this is a text
OK
Enter your command: GET
this is a text
Enter your command: TRANSLATE
THIS IS A TEXT
Enter your command: GET
THIS IS A TEXT
Enter your command: QUIT
I hope you can continue from there.
Another important point is that, you're using TCP (socket.SOCK_STREAM), so you can actually retain the connection after accepting it with s.accept(), and you should only close it when you have accomplished the task on that connection (accepting new connection has its overhead). Your current code will only be able to handle single client. But, I think for starter, this is good enough. After you've confident with this, you can try to handle more clients by using threading.