I'm looking to build a chat room in python at the moment and am struggling with direct messages as I'm using client.recv(2048) function in both my thread listening for messages from the server and trying to use client.recv() in my main function to receive a list of active users on the server. It seems the program will work sometimes and others will shift to the clientreceive function.
Thread started
# Starts thread for client receive
receive_thread = threading.Thread(target=client_receive)
receive_thread.start()
receive block
def client_receive():
while True:
try:
message = client.recv(2048).decode()
print(message)
except:
client.close()
break
main method (DM)
if msg_type == "DM":
# Sends C DM message to server
dm_msg = "C DM"
client.send(dm_msg.encode())
# Receives list of online users from server in client_receive
users = client.recv(2048).decode()
print(users)
# Client inputs username and message to server
target = input("Select user: ")
chat = input("> ")
chat_msg = "D " + target + "|||||" + chat
I attempted using locks in my main method, which did not seem to work. I expected my method to stay with my socket when I used lock.acquire(), however it still broke to the clientreceive function
Thanks
I'm currently working on the client part in a client-server socket programming, in order
to collect user input and receiving incoming messages from server at the same time (doesn't want to be stuck at input and not receiving or vice versa), i decided to use thread at first it worked pretty good, i'm currently implementing a timeout function e.g. closing the entire client side without manually typing input and couldn't do so (the timeout timing is calculated in the server and server can send a message), so i changed my thread to multiprocessing it can be terminated but it shows a EOF Error when it reads an input.
Just wondering is there a way to run my input_command() function at the same time as receiving messages and being able to terminate both?
def input_command():
while login:
command = input()
command_word = command.split(' ')
if command == 'logout':
clientSocket.send(command.encode('utf-8'))
print('user has logged out')
break
elif command == 'whoelse':
clientSocket.send(command.encode('utf-8'))
else:
clientSocket.send('giberish'.encode('utf-8'))
clientSocket.close()
server_port = int(sys.argv[1])
serverName = 'localhost'
clientSocket = socket(AF_INET, SOCK_STREAM)
clientSocket.connect((serverName, server_port))
login = False
once = False
while True:
received_message_encrypted = clientSocket.recv(1024)
received_message = received_message_encrypted.decode('utf-8')
if received_message == 'bye':
clientSocket.close()
login = False
thread_input.terminate()
break
if login == True and once == False:
once = True
thread_input = multiprocessing.Process(target=input_command)
thread_input.start()
use .close instead of .terminate in process
I've been given a summer assignment to create a chat room on python using sockets, using a main socket as the server that connects to all the other "client" sockets, each time a client sends a message to the server, the server sends it to everyone else but the client that sent it. The catch is that I need to make it so you can write messages and receive them at the same time, which is something I have no idea how to do so I took my friend's advice and tried to do it using multi-threading.
This is what I have right now, it's supposed to get more complicated but this is the very basic part:
client
import socket
import thread
import time
def receive_messages(recieve_socket):
while True:
print recieve_socket.recv(1024)
def send_messages(send_socket):
while True:
data = raw_input()
send_socket.send(data)
def main():
my_socket = socket.socket()
my_socket.connect(('127.0.0.1', 8822))
thread.start_new_thread(send_messages, (my_socket, ))
thread.start_new_thread(receive_messages, (my_socket, ))
time.sleep(1) #this delay lets the threads kick in, otherwise the thread count is zero and it crashes
while thread._count() > 1:
pass
if __name__ == '__main__':
main()
server
import socket
import select
waiting_messages = []
users = []
def add_new_user(user_socket):
new_socket, address = user_socket.accept()
users.append(new_socket)
print "A new user has joined"
def remove_user(user_socket):
users.remove(user_socket)
print "A user has left"
def send_waiting_messages(wlist):
for message in waiting_messages:
receiving_socket, data = message
if receiving_socket in wlist:
receiving_socket.send(data)
waiting_messages.remove(message)
def spread_messages(message, sending_user):
receiving_list = users
receiving_list.remove(sending_user)
for user in receiving_list:
waiting_messages.append((user, message))
print "A user has sent a message"
def main():
server_socket = socket.socket()
server_socket.bind(('0.0.0.0', 8822))
server_socket.listen(5)
# users = []
# messages_to_send = []
while True:
rlist, wlist, xlist = select.select([server_socket] + users, users, [])
for current_socket in rlist:
if current_socket is server_socket:
add_new_user(server_socket)
else:
data = current_socket.recv(1024)
if data == "quit":
remove_user(current_socket)
else:
spread_messages(data, current_socket)
send_waiting_messages(wlist)
if __name__ == '__main__':
main()
The issue is when I try to run it, the first message works fine, but after the second message the server just sends a lot of blank messages and stops sending the messages I send it.
I'd really appreciate help in the matter.
Thanks for the help guys, in the end I asked a friend of mine and he told me to use threading instead of select on the server and it worked great! I'll post the code later if anyone's interested.
I took a look at the various ZMQ messaging patterns and I'm not sure which one would do for my project. All I want to do is be able to connect to a server and send a command (the client never receive anything). On the server side, I want to be able to check if there is a message, if there is one, process it, else continue to do other stuff without blocking. That way, the server could continue to work even if there is no client connected.
#client.py
while(True):
select = raw_input()
if select == "1":
socket.send(msg1)
elif select == "2":
socket.send(msg2)
...
#server.py
while(True):
msg = socket.recv() #should not block
if msg == ...
#do stuff
#do other stuff
So which pattern should I use with ZMQ to do that? Example code would be appreciated.
First, since you want one-way communication with only one socket receiving messages, that generally means PUSH-PULL. Here is a version of the client:
import zmq
ctx = zmq.Context.instance()
s = ctx.socket(zmq.PUSH)
url = 'tcp://127.0.0.1:5555'
s.connect(url)
while True:
msg = raw_input("msg > ")
s.send(msg)
if msg == 'quit':
break
so a PUSH socket sends the messages we get from raw_input. It should be clear how to change that logic to generate the messages you want. A bit of bonus is that if you type 'quit', both the client and the server will quit.
There are a variety of ways to do the non-blocking server, depending on the complexity of your application. I'll show a few examples, from the most basic one to the most powerful / extensible.
All of these server examples assume this at the top, setting up the server's PULL socket:
import time
import zmq
ctx = zmq.Context.instance()
s = ctx.socket(zmq.PULL)
url = 'tcp://127.0.0.1:5555'
s.bind(url)
The first example is simple non-blocking recv, which raises a zmq.Again Exception if there are no messages ready to be received:
# server0.py
while True:
try:
msg = s.recv(zmq.NOBLOCK) # note NOBLOCK here
except zmq.Again:
# no message to recv, do other things
time.sleep(1)
else:
print("received %r" % msg)
if msg == 'quit':
break
But that pattern is pretty hard to extend beyond very simple cases. The second example uses a Poller, to check for events on the socket:
# server1.py
poller = zmq.Poller()
poller.register(s)
while True:
events = dict(poller.poll(0))
if s in events:
msg = s.recv()
print("received %r" % msg)
if msg == 'quit':
break
else:
# no message to recv, do other things
time.sleep(1)
In this toy example, this is very similar to the first. But, unlike the first, it is easy to extend to many sockets or events with further calls to poller.register, or passing a timeout other than zero to poller.poll.
The last example uses an eventloop, and actually registers a callback for when messages arrive. You can build very complex applications with this sort of pattern, and it is a fairly straightforward way to write code that only does work when there is work to be done.
# server2.py
from zmq.eventloop import ioloop
from zmq.eventloop.zmqstream import ZMQStream
def print_msg(msg):
print("received %r" % ' '.join(msg))
if msg[0] == 'quit':
ioloop.IOLoop.instance().stop()
# register the print_msg callback to be fired
# whenever there is a message on our socket
stream = ZMQStream(s)
stream.on_recv(print_msg)
# do other things in the meantime
tic = time.time()
def do_other_things():
print("%.3f" % (time.time() - tic))
pc = ioloop.PeriodicCallback(do_other_things, 1000)
pc.start()
# start the eventloop
ioloop.IOLoop.instance().start()
So that's a few basic ways to deal with zmq messages without blocking. You can grab these examples together as a gist.
I am currently working on a school project where the assignment, among other things, is to set up a threaded server/client system. Each client in the system is supposed to be assigned its own thread on the server when connecting to it. In addition i would like the server to run other threads, one concerning input from the command line and another concerning broadcasting messages to all clients. However, I can't get this to run as i want to. It seems like the threads are blocking each other. I would like my program to take inputs from the command line, at the "same time" as the server listens to connected clients, and so on.
I am new to python programming and multithreading, and allthough I think my idea is good, I'm not suprised my code doesn't work. Thing is I'm not exactly sure how I'm going to implement the message passing between the different threads. Nor am I sure exactly how to implement the resource lock commands properly. I'm going to post the code for my server file and my client file here, and I hope someone could help me with this. I think this actually should be two relative simple scripts. I have tried to comment on my code as good as possible to some extend.
import select
import socket
import sys
import threading
import client
class Server:
#initializing server socket
def __init__(self, event):
self.host = 'localhost'
self.port = 50000
self.backlog = 5
self.size = 1024
self.server = None
self.server_running = False
self.listen_threads = []
self.local_threads = []
self.clients = []
self.serverSocketLock = None
self.cmdLock = None
#here i have also declared some events for the command line input
#and the receive function respectively, not sure if correct
self.cmd_event = event
self.socket_event = event
def openSocket(self):
#binding server to port
try:
self.server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.server.bind((self.host, self.port))
self.server.listen(5)
print "Listening to port " + str(self.port) + "..."
except socket.error, (value,message):
if self.server:
self.server.close()
print "Could not open socket: " + message
sys.exit(1)
def run(self):
self.openSocket()
#making Rlocks for the socket and for the command line input
self.serverSocketLock = threading.RLock()
self.cmdLock = threading.RLock()
#set blocking to non-blocking
self.server.setblocking(0)
#making two threads always running on the server,
#one for the command line input, and one for broadcasting (sending)
cmd_thread = threading.Thread(target=self.server_cmd)
broadcast_thread = threading.Thread(target=self.broadcast,args=[self.clients])
cmd_thread.daemon = True
broadcast_thread.daemon = True
#append the threads to thread list
self.local_threads.append(cmd_thread)
self.local_threads.append(broadcast_thread)
cmd_thread.start()
broadcast_thread.start()
self.server_running = True
while self.server_running:
#connecting to "knocking" clients
try:
c = client.Client(self.server.accept())
self.clients.append(c)
print "Client " + str(c.address) + " connected"
#making a thread for each clientn and appending it to client list
listen_thread = threading.Thread(target=self.listenToClient,args=[c])
self.listen_threads.append(listen_thread)
listen_thread.daemon = True
listen_thread.start()
#setting event "client has connected"
self.socket_event.set()
except socket.error, (value, message):
continue
#close threads
self.server.close()
print "Closing client threads"
for c in self.listen_threads:
c.join()
def listenToClient(self, c):
while self.server_running:
#the idea here is to wait until the thread gets the message "client
#has connected"
self.socket_event.wait()
#then clear the event immidiately...
self.socket_event.clear()
#and aquire the socket resource
self.serverSocketLock.acquire()
#the below is the receive thingy
try:
recvd_data = c.client.recv(self.size)
if recvd_data == "" or recvd_data == "close\n":
print "Client " + str(c.address) + (" disconnected...")
self.socket_event.clear()
self.serverSocketLock.release()
return
print recvd_data
#I put these here to avoid locking the resource if no message
#has been received
self.socket_event.clear()
self.serverSocketLock.release()
except socket.error, (value, message):
continue
def server_cmd(self):
#this is a simple command line utility
while self.server_running:
#got to have a smart way to make this work
self.cmd_event.wait()
self.cmd_event.clear()
self.cmdLock.acquire()
cmd = sys.stdin.readline()
if cmd == "":
continue
if cmd == "close\n":
print "Server shutting down..."
self.server_running = False
self.cmdLock.release()
def broadcast(self, clients):
while self.server_running:
#this function will broadcast a message received from one
#client, to all other clients, but i guess any thread
#aspects applied to the above, will work here also
try:
send_data = sys.stdin.readline()
if send_data == "":
continue
else:
for c in clients:
c.client.send(send_data)
self.serverSocketLock.release()
self.cmdLock.release()
except socket.error, (value, message):
continue
if __name__ == "__main__":
e = threading.Event()
s = Server(e)
s.run()
And then the client file
import select
import socket
import sys
import server
import threading
class Client(threading.Thread):
#initializing client socket
def __init__(self,(client,address)):
threading.Thread.__init__(self)
self.client = client
self.address = address
self.size = 1024
self.client_running = False
self.running_threads = []
self.ClientSocketLock = None
def run(self):
#connect to server
self.client.connect(('localhost',50000))
#making a lock for the socket resource
self.clientSocketLock = threading.Lock()
self.client.setblocking(0)
self.client_running = True
#making two threads, one for receiving messages from server...
listen = threading.Thread(target=self.listenToServer)
#...and one for sending messages to server
speak = threading.Thread(target=self.speakToServer)
#not actually sure wat daemon means
listen.daemon = True
speak.daemon = True
#appending the threads to the thread-list
self.running_threads.append(listen)
self.running_threads.append(speak)
listen.start()
speak.start()
#this while-loop is just for avoiding the script terminating
while self.client_running:
dummy = 1
#closing the threads if the client goes down
print "Client operating on its own"
self.client.close()
#close threads
for t in self.running_threads:
t.join()
return
#defining "listen"-function
def listenToServer(self):
while self.client_running:
#here i acquire the socket to this function, but i realize I also
#should have a message passing wait()-function or something
#somewhere
self.clientSocketLock.acquire()
try:
data_recvd = self.client.recv(self.size)
print data_recvd
except socket.error, (value,message):
continue
#releasing the socket resource
self.clientSocketLock.release()
#defining "speak"-function, doing much the same as for the above function
def speakToServer(self):
while self.client_running:
self.clientSocketLock.acquire()
try:
send_data = sys.stdin.readline()
if send_data == "close\n":
print "Disconnecting..."
self.client_running = False
else:
self.client.send(send_data)
except socket.error, (value,message):
continue
self.clientSocketLock.release()
if __name__ == "__main__":
c = Client((socket.socket(socket.AF_INET, socket.SOCK_STREAM),'localhost'))
c.run()
I realize this is quite a few code lines for you to read through, but as I said, I think the concept and the script in it self should be quite simple to understand. It would be very much appriciated if someone could help me synchronize my threads in a proper way =)
Thanks in advance
---Edit---
OK. So I now have simplified my code to just containing send and receive functions in both the server and the client modules. The clients connecting to the server gets their own threads, and the send and receive functions in both modules operetes in their own separate threads. This works like a charm, with the broadcast function in the server module echoing strings it gets from one client to all clients. So far so good!
The next thing i want my script to do, is taking specific commands, i.e. "close", in the client module to shut down the client, and join all running threads in the thread list. Im using an event flag to notify the listenToServer and the main thread that the speakToServer thread has read the input "close". It seems like the main thread jumps out of its while loop and starts the for loop that is supposed to join the other threads. But here it hangs. It seems like the while loop in the listenToServer thread never stops even though server_running should be set to False when the event flag is set.
I'm posting only the client module here, because I guess an answer to get these two threads to synchronize will relate to synchronizing more threads in both the client and the server module also.
import select
import socket
import sys
import server_bygg0203
import threading
from time import sleep
class Client(threading.Thread):
#initializing client socket
def __init__(self,(client,address)):
threading.Thread.__init__(self)
self.client = client
self.address = address
self.size = 1024
self.client_running = False
self.running_threads = []
self.ClientSocketLock = None
self.disconnected = threading.Event()
def run(self):
#connect to server
self.client.connect(('localhost',50000))
#self.client.setblocking(0)
self.client_running = True
#making two threads, one for receiving messages from server...
listen = threading.Thread(target=self.listenToServer)
#...and one for sending messages to server
speak = threading.Thread(target=self.speakToServer)
#not actually sure what daemon means
listen.daemon = True
speak.daemon = True
#appending the threads to the thread-list
self.running_threads.append((listen,"listen"))
self.running_threads.append((speak, "speak"))
listen.start()
speak.start()
while self.client_running:
#check if event is set, and if it is
#set while statement to false
if self.disconnected.isSet():
self.client_running = False
#closing the threads if the client goes down
print "Client operating on its own"
self.client.shutdown(1)
self.client.close()
#close threads
#the script hangs at the for-loop below, and
#refuses to close the listen-thread (and possibly
#also the speak thread, but it never gets that far)
for t in self.running_threads:
print "Waiting for " + t[1] + " to close..."
t[0].join()
self.disconnected.clear()
return
#defining "speak"-function
def speakToServer(self):
#sends strings to server
while self.client_running:
try:
send_data = sys.stdin.readline()
self.client.send(send_data)
#I want the "close" command
#to set an event flag, which is being read by all other threads,
#and, at the same time set the while statement to false
if send_data == "close\n":
print "Disconnecting..."
self.disconnected.set()
self.client_running = False
except socket.error, (value,message):
continue
return
#defining "listen"-function
def listenToServer(self):
#receives strings from server
while self.client_running:
#check if event is set, and if it is
#set while statement to false
if self.disconnected.isSet():
self.client_running = False
try:
data_recvd = self.client.recv(self.size)
print data_recvd
except socket.error, (value,message):
continue
return
if __name__ == "__main__":
c = Client((socket.socket(socket.AF_INET, socket.SOCK_STREAM),'localhost'))
c.run()
Later on, when I get this server/client system up and running, I will use this system on some elevator models we have here on the lab, with each client receiving floor orders or "up" and "down" calls. The server will be running an distribution algorithm and updating the elevator queues on the clients that are most appropriate for the requested order. I realize it's a long way to go, but I guess one should just take one step at the time =)
Hope someone has the time to look into this. Thanks in advance.
The biggest problem I see with this code is that you have far too much going on right away to easily debug your problem. Threading can get extremely complicated because of how non-linear the logic becomes. Especially when you have to worry about synchronizing with locks.
The reason you are seeing clients blocking on each other is because of the way you are using your serverSocketLock in your listenToClient() loop in the server. To be honest this isn't exactly your problem right now with your code, but it became the problem when I started to debug it and turned the sockets into blocking sockets. If you are putting each connection into its own thread and reading from them, then there is no reason to use a global server lock here. They can all read from their own sockets at the same time, which is the purpose of the thread.
Here is my recommendation to you:
Get rid of all the locks and extra threads that you don't need, and start from the beginning
Have the clients connect as you do, and put them in their thread as you do. And simply have them send data every second. Verify that you can get more than one client connecting and sending, and that your server is looping and receiving. Once you have this part working, you can move on to the next part.
Right now you have your sockets set to non-blocking. This is causing them all to spin really fast over their loops when data is not ready. Since you are threading, you should set them to block. Then the reader threads will simply sit and wait for data and respond immediately.
Locks are used when threads will be accessing shared resources. You obviously need to for any time a thread will try and modify a server attribute like a list or a value. But not when they are working on their own private sockets.
The event you are using to trigger your readers doesn't seem necessary here. You have received the client, and you start the thread afterwards. So it is ready to go.
In a nutshell...simplify and test one bit at a time. When its working, add more. There are too many threads and locks right now.
Here is a simplified example of your listenToClient method:
def listenToClient(self, c):
while self.server_running:
try:
recvd_data = c.client.recv(self.size)
print "received:", c, recvd_data
if recvd_data == "" or recvd_data == "close\n":
print "Client " + str(c.address) + (" disconnected...")
return
print recvd_data
except socket.error, (value, message):
if value == 35:
continue
else:
print "Error:", value, message
Backup your work, then toss it - partially.
You need to implement your program in pieces, and test each piece as you go. First, tackle the input part of your program. Don't worry about how to broadcast the input you received. Instead worry that you are able to successfully and repeatedly receive input over your socket. So far - so good.
Now, I assume you would like to react to this input by broadcasting to the other attached clients. Well too bad, you can't do that yet! Because, I left one minor detail out of the paragraph above. You have to design a PROTOCOL.
What is a protocol? It's a set of rules for communication. How does your server know when the client had finished sending it's data? Is it terminated by some special character? Or perhaps you encode the size of the message to be sent as the first byte or two of the message.
This is turning out to be a lot of work, isn't it? :-)
What's a simple protocol. A line-oriented protocol is simple. Read 1 character at a time until you get to the end of record terminator - '\n'. So, clients would send records like this to your server --
HELO\n
MSG DAVE Where Are Your Kids?\n
So, assuming you have this simple protocol designed, implement it. For now, DON'T WORRY ABOUT THE MULTITHREADING STUFF! Just worry about making it work.
Your current protocol is to read 1024 bytes. Which may not be bad, just make sure you send 1024 byte messages from the client.
Once you have the protocol stuff setup, move on to reacting to the input. But for now you need something that will read input. Once that is done, we can worry about doing something with it.
jdi is right, you have too much program to work with. Pieces are easier to fix.