I have a short server script which sends a byte to a client informing it what game should be put on a screen. It works for one client but I want to send it to more, but can only send it to the client which connected last, and I cannot figure out why? Do I need to use multiple threads? The code I have is:
import socket
def gameChose():
if nb=='Game1':
conn.sendall(b'Game1')
if nb=='Game2':
conn.sendall(b'Game2')
if nb=='Game3':
conn.sendall(b'Game3')
HOST = ''
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(2)
for x in range (0,2):
conn, addr = s.accept()
print ('Connected by', addr)
while 1:
nb = input('What kind of game would you like to play?')
gameChose()
I have placed a for loop because I know how many clients are going to connect. Thanks in advance.
Related
I copied the echo server example from the python documentation and it's working fine. But when I edit the code, so it wont send the data back to the client, the socket.recv() method doesn't return when it's called the second time.
import socket
HOST = ''
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(b'ok')
conn.close()
In the original version from the python documentation the while loop is slightly different:
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
Client's code:
import socket
HOST = 'localhost'
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
data = s.recv(1024)
s.close()
print('Received', repr(data))
TCP sockets are streams of data. There is no one-to-one correlation between send calls on one side and receive calls on the other. There is a higher level correlation based on the protocol you implement. In the original code, the rule was that the server would send exactly what it received until the client closed the incoming side of the connection. Then the server closed the socket.
With your change, the rules changed. Now the server keeps receiving and discarding data until the client closes the incoming side of the connection. Then the server sends "ok" and closes the socket.
A client using the first rule hangs because its expecting data before it closes the socket. If it wants to work with this new server rule, it has to close its outgoing side of the socket to tell the server its done, and then it can get the return data.
I've updated the client and server to shutdown parts of the connection and also have the client do multiple recv's in case the incoming data is fragmented. Less complete implementations seem to work for small payloads because you are unlikely to get fragmentation, but break horribly in real production code.
server
import socket
HOST = ''
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(b'ok')
conn.shutdown(socket.SHUT_WR)
conn.close()
client
import socket
HOST = 'localhost'
PORT = 50007
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
s.shutdown(socket.SHUT_WR)
data = b''
while True:
buf = s.recv(1024)
if not buf:
break
data += buf
s.close()
print('Received', repr(data))
The number of receive and send operations have to match because they are blocking. This is the flow diagram for your code:
Server listen
Client connect
Server receive (this waits until a message arrives at the server) [1]
Client send 'Hello world' (received by [1])
Server receive (because there was data received) [2]
Client receive [3]
Because the server and the client are blocked now, no program can continue any further.
The fix would be to remove the client's receive call because you removed the server's send call.
I'm trying to:
Connect to a server/port
Listen for x seconds
Receive user input
Send user input to server
Go back to step 2
So far, I've written the following code, but it's not working properly receiving input after the first send. Any help would be greatly appreciated.
import socket
import select
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(('domain.com', 1234))
client_socket.setblocking(0)
timeout = 5
while True:
while True:
ready = select.select([client_socket], [], [], timeout)
if ready[0]:
data = client_socket.recv(4096)
print data
else:
break
data = raw_input("Enter input:")
client_socket.send(data)
You need to have separate server side code and client side code. This article has been referred.
Server binds to a port and listens for clients
server.py
import select
import socket
# Create a TCP/IP socket
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setblocking(0)
# Bind the socket to the port
server_address = ('localhost', 1234)
server.bind(server_address)
# Listen for incoming connections
server.listen(5)
# Sockets from which we expect to read
inputs = [ server ]
# Sockets to which we expect to write
outputs = [ ]
while inputs:
readable, writable, exceptional = select.select(inputs, outputs, inputs)
# Handle inputs
for s in readable:
if s is server:
# A "readable" server socket is ready to accept a connection
connection, client_address = s.accept()
connection.setblocking(0)
inputs.append(connection)
else:
data = s.recv(1024)
if data:
print "Receiving data from client"
print data
else:
inputs.remove(s)
s.close()
Client first establishes a connection with the server and then keeps on sending user input to the server.
client.py
import socket
server_address = ('domain.com', 1234)
# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(server_address)
while True:
data = raw_input("Enter input:")
sock.send(data)
Open terminal.
Run server in background:
python server.py &
Run client after that:
python client.py
Here is the server:
import socket
HOST = '127.0.0.1'
PORT = 4444
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(5)
conn, addr = s.accept()
print addr, 'connected.'
while True:
data = conn.recv(1024)
print '> ', data
reply = raw_input(">> ")
conn.sendall(reply)
if reply == 'bye':
break
conn.close()
And here is the client:
import socket
HOST = '127.0.0.1'
PORT = 4444
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
while True:
message = raw_input("> ")
s.send(message)
reply = s.recv(1024)
print ">> ", repr(reply)
if message == 'bye':
break
s.close()
What is the most efficient way to upgrade this code to support multiple instances, and more importantly: how could I assign names (nicknames) to all clients and make it so clients could type whenever they want? I tried to use Threading, but that was a huge disaster .
Multiple client
For multiple client connection, you need to have some non-linear execution.
You can either use coroutines or threads to achieve this.
Python 3 comes with asyncio, library that uses coroutines (and lot of other features) to emulate multithreading. I suggest you look into this.
You can also use threads, it's not that complicated. Whenever a client connects to your server, you just have to create a new thread to execute your function. Python official documentation should help you achieve that.
Nickname
Whenever a client connects to your server, you could instantiate a User object in the newly created thread with your client information, so that each thread has its own User instance.
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)
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.