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Connection between client and server fails, send/recv doesnt work (python)

I have put together a server and client code to use in a messaging app. When I run the server and starts one client, everything works fine. When I start a second client, I can send messages from the first client and the second client will recieve them. I can send one message from the second client and the first client will recieve this first message. But after this message, the second client can not send or the server can not receive the data for some reason. The first client can still send messages.
I dont know where the mistake is, but I believe either the client can not .send() or the server can not .recv().
(I am quite new to programming so the code might be quite messy and not the most understandeble, and maybe there are several flaws...)
The server code
import socket
from _thread import *
import sys
HOST = "127.0.0.1"
PORT = 12000
client_socket = set()
def threaded(conn):
while True:
try:
data = conn.recv(1024).decode()
if not data:
print("Lost connection")
break
for conn in client_socket :
conn.send(data.encode())
except:
break
print("Gone")
conn.close()
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(5)
print("Server is up and running")
while True:
conn, addr = s.accept()
print("Connected to", addr)
client_socket .add(conn)
start_new_thread(threaded, (conn, ))
The client code
import threading
import socket, sys
HOST = "127.0.0.1"
PORT = 12000
check= ""
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
def background():
while True:
answer= s.recv(1024).decode()
if check!= answer and answer!= "":
print(answer)
threading1 = threading.Thread(target=background)
threading1.daemon = True
threading1.start()
while True:
message= input()
if message!= "":
s.send(message.encode())
check = message

Python socket client works only for one iteration

I am trying to implement sockets with python.the following code works well without the while loop..but with the while loop, for the second iteration , it gets stuck in s.sendall().could you please suggest how to fix this ?
def main():
host = socket.gethostname()
port = 11111
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((host, port))
print "Connected to Server!"
while True:
print "Enter your Command:"
command = raw_input()
if(command):
try:
sock.sendall(repr(command))
except socket.error:
print "Socket Error Occured"
data = sock.recv(1024)
if data:
print('Received', repr(data))
else:
print "No Data"
else:
os.system("clear")
sock.close()
if __name__ == "__main__":
main()

Hello
I don't have all the information I need to make this post as
informed as I'd like, however I can make some educate
d guesses and try my best to explain what I think is going wrong. Are you ready?? Lets get into it.
So,
You start off by making a tcp socket and then connecting to a server hosted locally on port 11111
host = socket.gethostname()
port = 11111
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((host, port))
next you enter a loop
while True:
#input command, request eval
Here your goal is to take user input and send it to a server to eval. You do that with
#get user input
print "Enter your Command:"
command = raw_input()
#send command to server for eval
sock.sendall(repr(command))
#receive then print eval
data = sock.recv(1024)
print('Received', repr(data))
this works and sends commands as you'd expect, although sending repr(command) might not be what you want to send
command = "1+1"
eval(command)
//2
eval(repr(command))
//'1+1'
Now
Here is where I have to make some assumptions
Early on you connected to a server
sock.connect((host, port))
I'm assuming that the server accepts your connection evals your command and sends the answer back. Something like
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind('localhost',11111)
sock.listen()
while True:
conn, addr = sock.accept()
command = conn.recv(1024)
sock.sendall(eval(command))
If this is the case then your connection might fail because your eval server runs eval once and then accepts a new connection.
That means that your client can no longer send to, or recieve data from, the server
I hope this helps.

TCP client server not receiving any data from each other

I have written the following TCP client and server using python socket module. However, after I run them, no output is being given. It seems that
the program is not able to come out of the while loop in the recv_all method
Server:
import socket
def recv_all(sock):
data = []
while True:
dat = sock.recv(18)
if not dat:
break
data.append(dat)
return "".join(data)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
HOST = '127.0.0.1'
PORT = 45678
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((HOST, PORT))
sock.listen(1)
print "listening at", sock.getsockname()
while True:
s, addr = sock.accept()
print "receiving from", addr
final = recv_all(s)
print "the client sent", final
s.sendall("hello client")
s.close()
Client :
import socket
def recv_all(sock):
data=[]
while True:
dat=sock.recv(18)
if not dat:
break
data.append(dat)
return "".join(data)
sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
PORT=45678
HOST='127.0.0.1'
sock.connect((HOST,PORT))
sock.sendall("hi server")
final=recv_all(sock)
print "the server sent",final

Because in server file you use an endless loop in another. I suggest you to edit recv_all method in both files this way:
def recv_all(sock):
data = []
dat = sock.recv(18)
data.append(dat)
return "".join(data)
But after edit like this your server stays on until KeyInterrupt, while you should run client file everytime you want to send data. If you want an automatically send/receive between server and client, I offer you try threading.

Python server programming

I am trying a little client server project to get me into network programming but I seem to have got stuck at the first hurdle. I cant seem to get past getting the first line of data only even if its a new connection.
#!/usr/bin/python
import socket
s = socket.socket()
host = '192.168.0.233' # Test Server
port = 7777
s.bind((host, port))
s.listen(5)
while True:
c, addr = s.accept()
print 'Got connection from', addr
data = c.recv(2048)
print(data)
If I telnet to the host running the server, the connection opens fine and I see on the server Got connection from addr, but I also only see the first line of data when I sent 4 lines of data,
I thought because its in a loop it should now always be looking for data?
I know im doing something wrong but unsure what.
Im using Python 2.6.6

recv needs to be in a loop too, at the moment your code is receiving some data and then waiting for a new connection.
https://docs.python.org/2/library/socket.html#example has an example of socket.recv in a loop.

Try this:
#!/usr/bin/python
import socket
import threading
def listenForClients(sock):
while True:
client, address = sock.accept()
client.settimeout(5)
threading.Thread( target = listenToClient, args = (client,address) ).start()
def listenToClient(client, address):
size = 2048
while True:
try:
data = client.recv(size)
if data:
response = "Got connection"
client.send(response)
else:
raise error('Client disconnected')
except:
client.close()
return False
def main(host, port):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind((host, port))
sock.listen(5)
listenForClients(sock)
if __name__ == "__main__":
main('192.168.0.233',7777)
Here I use a thread for each client. The problem that you have with having Socket.accept() in the loop is that it blocks meaning that concurrent access won't work and you'll only be able to talk to one client at a time.
Try running it in the background and sending it messages with:
#!/usr/bin/python
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('192.168.0.233',7777))
vwhile True:
data = raw_input("enter a message: ")
sock.send(data)
print sock.recv(2048)

Sending string via socket (python)

I have two scripts, Server.py and Client.py.
I have two objectives in mind:
To be able to send data again and again to server from client.
To be able to send data from Server to client.
here is my Server.py :
import socket
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "192.168.1.3"
port = 8000
print (host)
print (port)
serversocket.bind((host, port))
serversocket.listen(5)
print ('server started and listening')
while 1:
(clientsocket, address) = serversocket.accept()
print ("connection found!")
data = clientsocket.recv(1024).decode()
print (data)
r='REceieve'
clientsocket.send(r.encode())
and here is my client :
#! /usr/bin/python3
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host ="192.168.1.3"
port =8000
s.connect((host,port))
def ts(str):
s.send('e'.encode())
data = ''
data = s.recv(1024).decode()
print (data)
while 2:
r = input('enter')
ts(s)
s.close ()
The function works for the first time ('e' goes to the server and I get return message back), but how do I make it happen over and over again (something like a chat application) ?
The problem starts after the first time. The messages don't go after the first time.
what am I doing wrong?
I am new with python, so please be a little elaborate, and if you can, please give the source code of the whole thing.

import socket
from threading import *
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = "192.168.1.3"
port = 8000
print (host)
print (port)
serversocket.bind((host, port))
class client(Thread):
def __init__(self, socket, address):
Thread.__init__(self)
self.sock = socket
self.addr = address
self.start()
def run(self):
while 1:
print('Client sent:', self.sock.recv(1024).decode())
self.sock.send(b'Oi you sent something to me')
serversocket.listen(5)
print ('server started and listening')
while 1:
clientsocket, address = serversocket.accept()
client(clientsocket, address)
This is a very VERY simple design for how you could solve it.
First of all, you need to either accept the client (server side) before going into your while 1 loop because in every loop you accept a new client, or you do as i describe, you toss the client into a separate thread which you handle on his own from now on.

client.py
import socket
s = socket.socket()
s.connect(('127.0.0.1',12345))
while True:
str = raw_input("S: ")
s.send(str.encode());
if(str == "Bye" or str == "bye"):
break
print "N:",s.recv(1024).decode()
s.close()
server.py
import socket
s = socket.socket()
port = 12345
s.bind(('', port))
s.listen(5)
c, addr = s.accept()
print "Socket Up and running with a connection from",addr
while True:
rcvdData = c.recv(1024).decode()
print "S:",rcvdData
sendData = raw_input("N: ")
c.send(sendData.encode())
if(sendData == "Bye" or sendData == "bye"):
break
c.close()
This should be the code for a small prototype for the chatting app you wanted.
Run both of them in separate terminals but then just check for the ports.

This piece of code is incorrect.
while 1:
(clientsocket, address) = serversocket.accept()
print ("connection found!")
data = clientsocket.recv(1024).decode()
print (data)
r='REceieve'
clientsocket.send(r.encode())
The call on accept() on the serversocket blocks until there's a client connection. When you first connect to the server from the client, it accepts the connection and receives data. However, when it enters the loop again, it is waiting for another connection and thus blocks as there are no other clients that are trying to connect.
That's the reason the recv works correct only the first time. What you should do is find out how you can handle the communication with a client that has been accepted - maybe by creating a new Thread to handle communication with that client and continue accepting new clients in the loop, handling them in the same way.
Tip: If you want to work on creating your own chat application, you should look at a networking engine like Twisted. It will help you understand the whole concept better too.