I'm trying to do a client server exercise in Python and it has to be concurrent, so basically I got a main server and 3 other download servers. These download servers connect just fine to the main one but whenever I want to interact with them I just can't. I tried to cycle through the threads and execute a simple function that sends a different message from the main server to each of the download ones. The problem is that it only sends the message to the last one it cycles through, and it doesn't even send the right message, it sends the message meant to be delivered to the first server to the last one.
So here's my code:
import socket
from threading import Thread
from SocketServer import ThreadingMixIn
import logging
# Multithreaded Python server : TCP Server Socket Thread Pool
class ClientThread(Thread):
def __init__(self,ip,port):
Thread.__init__(self)
self.ip = ip
self.port = port
print "[+] New server socket thread started for " + ip + ":" + str(port)
def run(self):
while True :
data = conn.recv(2048)
print "Server received data:", data
#MESSAGE = raw_input("Multithreaded Python server : Enter Response from Server/Enter exit:")
if not data:
break
if data == 'exit':
break
#conn.send(MESSAGE) # echo
class DServerThread(Thread):
def __init__(self,ip,port):
Thread.__init__(self)
self.ip = ip
self.port = port
def run(self):
while True :
data = conn.recv(2048)
print "Server received data:", data
if not data:
break
if data == 'exit':
break
#conn.send(MESSAGE) # echo
def sendmsg(self,str):
conn.send(str)
# Multithreaded Python server : TCP Server Socket Program Stub
TCP_IP = '0.0.0.0'
TCP_PORT = 2004
sport = 5000
BUFFER_SIZE = 20
dServer=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
dServer.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
dServer.bind((TCP_IP, sport))
tcpServer = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpServer.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcpServer.bind((TCP_IP, TCP_PORT))
cthreads = [] #client threads
sthreads = [] #download server threads
controlthreads = [] #Threads to manage the background processes
for i in range(1, 4):
dServer.listen(3)
(conn, (ip,port)) = dServer.accept()
newthread = DServerThread(ip,port)
newthread.start()
sthreads.append(newthread)
for t in sthreads:
print t.getName()
t.sendmsg(t.getName())
The problem to me is on that last loop, but I don't quite get why.
TL;DR: Last loop isn't working as intended, it seems to only execute the function on the last iteration and send the message meant for the first thread.
Related
Having a small problem with a multithreaded socket server in Python 3. I can't seem to start my socket listening in its own thread. I'm probably way off base.
Borrowed the code here: How to make a simple multithreaded socket server in Python that remembers clients
But I need to listen for clients within a thread or at least in the background. Can't figure out what I'm doing wrong.
Here's my code:
import socket
from threading import Thread
from cmd import Cmd
class ThreadedServer(Thread):
def __init__(self):
self.host = "127.0.0.1"
self.port = int(8080)
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.sock.bind((self.host, self.port))
def listen(self):
self.sock.listen(5)
print("[Info]: Listening for connections on {0}, port {1}".format(self.host,self.port))
while True:
print("Hello?") # Just debug for now
client, address = self.sock.accept()
client.settimeout(60)
threading.Thread(target = self.listenToClient,args = (client,address)).start()
def listenToClient(self, client, address):
size = 1024
while True:
try:
data = client.recv(size)
if data:
# Set the response to echo back the recieved data
response = data
client.send(response)
else:
raise error('Client disconnected')
except:
client.close()
return False
class CommandInput(Cmd):
# Able to accept user input here but is irrelevant right now
pass
print("[Info]: Loading complete.")
clientThread = ThreadedServer().listen()
clientThread.start()
print("[Info]: Server ready!")
prompt = CommandInput()
prompt.prompt = '> '
prompt.cmdloop("[Info]: Type \'help\' for a list of commands and their descriptions/use")
As you can see I have some code after my listening part where I need to be able to accept input on the terminal. However, the code never gets there.
Here's the output quite simply:
[Info]: Loading complete.
[Info]: Listening for connections on 127.0.0.1, port 8080
Hello?
I'm expecting:
[Info]: Loading complete.
[Info]: Listening for connections on 127.0.0.1, port 8080
Hello?
[Info]: Type \'help\' for a list of commands and their descriptions/use
>
with a cursor ready for me to type.
So how can I properly get my program to listen for clients in that loop in a proper thread so that I can enter prompts at the command line and process user input (for example one of the commands I want to implement is that of a client "send" which I would be able to send debug information to connected clients)
Thanks for any assistance you can provide.
This may not be the ideal structure for setting up what you want, but seems to solve the requirement you stated.
After launching this script on a terminal, you can make sample client connections by opening one, or more, browser tabs to localhost:8080
import socket
from threading import Thread
from cmd import Cmd
# basic threading tutorial: https://www.tutorialspoint.com/python3/python_multithreading.htm
class ThreadedServer(Thread):
def __init__(self):
Thread.__init__(self) # change here
self.host = "127.0.0.1"
self.port = int(8080)
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.sock.bind((self.host, self.port))
def run(self): # change here
self.sock.listen(5)
print("[Info]: Listening for connections on {0}, port {1}".format(self.host,self.port))
while True:
print("Hello?") # Just debug for now
client, address = self.sock.accept()
client.settimeout(60)
Thread(target = self.listenToClient, args = (client,address)).start() # change here
def listenToClient(self, client, address):
size = 1024
while True:
try:
data = client.recv(size)
if data:
# Set the response to echo back the recieved data
response = data
client.send(response)
else:
raise error('Client disconnected')
except:
client.close()
return False
class CommandInput(Cmd):
# Able to accept user input here but is irrelevant right now
pass
if __name__ == "__main__":
print("[Info]: Loading complete.")
server = ThreadedServer() # change here
server.start() # change here
print("[Info]: Server ready!")
prompt = CommandInput()
prompt.prompt = '> '
prompt.cmdloop("[Info]: Type \'help\' for a list of commands and their descriptions/use")
I have the following server program in Python which simulates a chat-room. The code accepts connections from clients and for each of them it launches a new thread. This thread will wait for messages from this client. The messages can be L so that the server will respond with a list of connected clients, ip:port msg the server will send the message msg to the client ip:port.
On client side there will be 2 threads, one for receiving messages from the server, the other for sending.
import socket
from threading import Thread
#from SocketServer import ThreadingMixIn
import signal
import sys
import errno
EXIT = False
address = []
address2 = []
# handler per il comando Ctrl+C
def sig_handler(signum, frame):
if (signum == 2):
print("Called SIGINT")
EXIT = True
signal.signal(signal.SIGINT, sig_handler) # setto l'handler per i segnali
# Multithreaded Python server : TCP Server Socket Thread Pool
class ClientThread(Thread):
def __init__(self,conn,ip,port):
Thread.__init__(self)
self.conn = conn
self.ip = ip
self.port = port
print ("[+] New server socket thread started for " + ip + ":" + str(port))
def run(self):
while True:
data = self.conn.recv(1024)
print ("Server received data:", data)
if (data=='L'):
#print "QUI",address2
tosend = ""
for i in address2:
tosend = tosend + "ip:"+str(i[0]) + "port:"+str(i[1])+"\n"
self.conn.send(tosend)
#mandare elenco client connessi
else:
#manda ip:port msg
st = data.split(" ")
msg = st[1:]
msg = ' '.join(msg)
print ("MSG 2 SEND: ",msg)
ipport = st[0].split(":")
ip = ipport[0]
port = ipport[1]
flag = False
print ("Address2:",address2)
print ("ip:",ip)
print ("port:",port)
for i in address2:
print (i[0],ip,type(i[0]),type(ip),i[1],type(i[1]),port,type(port))
if str(i[0])==str(ip) and str(i[1])==str(port):
i[2].send(msg)
self.conn.send("msg inviato")
flag = True
break
if flag == False:
self.conn.send("client non esistente")
if __name__ == '__main__':
# Multithreaded Python server : TCP Server Socket Program Stub
TCP_IP = '127.0.0.1'
TCP_PORT = 2004
TCP_PORTB = 2005
BUFFER_SIZE = 1024 # Usually 1024, but we need quick response
tcpServer = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpServer.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcpServer.bind((TCP_IP, TCP_PORT))
tcpServerB = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpServerB.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcpServerB.bind((TCP_IP, TCP_PORTB))
threads = []
tcpServer.listen(4)
tcpServerB.listen(4)
while True:
print("Multithreaded Python server : Waiting for connections from TCP clients...")
try:
(conn, (ip,port)) = tcpServer.accept()
except socket.error as e: #(code, msg):
if e.errno != errno.EINTR:
raise
else:
break
address.append((ip,port,conn))
(conn2, (ip2,port2)) = tcpServerB.accept()
address2.append((ip2,port2,conn2))
newthread = ClientThread(conn,ip,port)
newthread.start()
threads.append(newthread)
if EXIT==True:
break
print ("SERVER EXIT")
for t in threads:
t.join()
The code has a signal handler for SIGINT to make the exit cleaner (closing connections, sending a message to the client (still to be implemented) and so on ). The handler writes a global flag EXIT to make the infinite loops terminate.
The code runs both in Python2 and Python3. However there are some problems with SIGINT signal generated by CTRL-C. When there is no client connected the program launched with Python2 exits correctly while the one in Python3 does not. Why this behavioural difference?
Considering only running the program in Python2, when a client connects and I press CTRL-C, the main while exits, like the signal is catched always by the main thread and this interrupts the blocking system call accept. However the other threads do not, I think because of the blocking underlying system call data = self.conn.recv(1024). In C I would block SIGINT signals for one thread and then call pthread_cancel from the other thread. How to exit from all threads when SIGINT is generated in Python?
The client program that for the moment works in Python2 only and suffers from the same problem is:
# Python TCP Client A
import socket
from threading import Thread
class ClientThread(Thread):
def __init__(self,conn):
Thread.__init__(self)
self.conn = conn
def run(self):
while True:
data = self.conn.recv(1024)
print "Ricevuto msg:",data
host = socket.gethostname()
print "host:",host
port = 2004
portB = 2005
BUFFER_SIZE = 2000
tcpClientA = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpClientB = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpClientA.connect(('127.0.0.1', port))
tcpClientB.connect(('127.0.0.1', portB))
newthread = ClientThread(tcpClientB)
newthread.start()
while(True):
msg = raw_input("Inserisci comando: ")
tcpClientA.send (msg)
data = tcpClientA.recv(BUFFER_SIZE)
print "data received:",data
tcpClientA.close()
As for the difference in behavior with accept() in Python 3, look at the full description in the docs. I think this is the key statement:
Changed in version 3.5: If the system call is interrupted and the signal handler does not raise an exception, the method now retries the system call instead of raising an InterruptedError exception (see PEP 475 for the rationale).
The other problem, stated in your penultimate sentence:
How to exit from all threads when SIGINT is generated in Python 2?
Take a look at the threading documentation:
A thread can be flagged as a “daemon thread”. The significance of this flag is that the entire Python program exits when only daemon threads are left. The initial value is inherited from the creating thread. The flag can be set through the daemon property.
I would like to write a very simple rock-paper-scissors game in Python. I would like to have 1 server and 2 clients. After connecting to the server, the server should send a message to each client to choose (r/p/s). After this, each client should send back their choice and the server then decides about the winner, and then it informs the clients about the winner.
This is what I have so far:
This is the server.py
import socket
from threading import Thread
class ClientThread(Thread):
def __init__(self, ip, port):
Thread.__init__(self)
self.ip = ip
self.port = port
print("[+] New server socket thread started for " + ip + ":" + str(port))
def run(self):
while True:
data = conn.recv(1024).decode()
print("Server received data:", data)
MESSAGE = input("Server response: ")
if MESSAGE == 'exit':
break
conn.send(MESSAGE.encode())
TCP_IP = '0.0.0.0'
TCP_PORT = 2004
BUFFER_SIZE = 1024
tcpServer = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpServer.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcpServer.bind((TCP_IP, TCP_PORT))
threads = []
while True:
tcpServer.listen(4)
print("Multithreaded Python server : Waiting for connections from TCP clients...")
(conn, (ip, port)) = tcpServer.accept()
newthread = ClientThread(ip, port)
newthread.start()
threads.append(newthread)
for t in threads:
t.join()
This is clientA.py:
import socket
host = socket.gethostname()
port = 2004
BUFFER_SIZE = 1024
MESSAGE = input("tcpClientA:")
tcpClientA = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpClientA.connect((host, port))
while MESSAGE != 'exit':
tcpClientA.send(MESSAGE.encode())
data = tcpClientA.recv(BUFFER_SIZE).decode()
print(" ClientA received data:", data)
MESSAGE = input("tcpClientA:")
tcpClientA.close()
This is clientB.py:
import socket
host = socket.gethostname()
port = 2004
BUFFER_SIZE = 1024
MESSAGE = input("tcpClientB:")
tcpClientB = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpClientB.connect((host, port))
while MESSAGE != 'exit':
tcpClientB.send(MESSAGE.encode())
data = tcpClientB.recv(BUFFER_SIZE).decode()
print(" ClientB received data:", data)
MESSAGE = input("tcpClientB:")
tcpClientB.close()
In this code, however, I can only send messages to the server and it can respond. Unfortunately, I don't know, how I can send messages to a specific client in this case. (I need to send different messages to the winner and to the loser).
First, this is not a trivial exercise and it will require a decent understanding of how threads work and how to work with them in Python in particular. What you seem to be missing at the moment is a way of orchestrating the communication from the 2 clients and of keeping track of what each client played so you can decide which client wins.
What currently happens is that when tcpClientA.connect((host, port)) runs on client A, (conn, (ip, port)) = tcpServer.accept() gets unblocked in the server. This creates a new instance of your ClientThread class and the new thread starts listening for data to be sent by client A on the connection. When client B runs, the same happens and you now have 2 threads running and listening for data but no way of knowing which plays what.
What I would suggest is to introduce a new class that will represent the game itself. That class will get the messages from both client and respond to each accordingly. What you will also need is a way of waiting for both clients to have played their turn before being able to decide who wins and what to send to each.
One way to do it would be with Barrier objects.
I'm trying to create a simple python chat interface however when two clients are connected to the server, the first clients console prints blank spaces as quick as possible and causes a max recursion depth error while the second client still works fine. The server code only sends data when its not blank so i'm not sure why it does this.
Server code:
import socket
from threading import Thread
from socketserver import ThreadingMixIn
class ClientThread(Thread):
def __init__(self,ip,port):
Thread.__init__(self)
self.ip = ip
self.port = port
print("[+] New thread started for "+ip+": "+str(port))
def run(self):
while True:
data = conn.recv(1024).decode()
if not data: break
if data == "/exit":
print("Connection for "+ip+" closed.")
data = "Connection closed."
conn.send(data.encode())
break
else:
print("received data: ", data)
if data != " ":
conn.send(data.encode())
print("connection "+ip+" force closed.")
TCP_IP = socket.gethostname()
TCP_PORT = 994
BUFFER_SIZE = 1024
tcpsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcpsock.bind((TCP_IP, TCP_PORT))
threads = []
while True:
tcpsock.listen(4)
(conn, (ip,port)) = tcpsock.accept()
newthread = ClientThread(ip,port)
newthread.start()
threads.append(newthread)
for t in threads:
t.join()
Client code:
import socket
import threading
from threading import Thread
TCP_IP = socket.gethostname()
TCP_PORT = 994
BUFFER_SIZE = 1024
name = str(input("Input username: "))
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
def recv():
while True:
data = s.recv(BUFFER_SIZE).decode()
if not data: break
print(data)
recv()
def send():
message = str(input())
if message != "/exit":
message = name + ": " + message
s.send(message.encode())
send()
if __name__ == "__main__":
Thread(target = recv).start()
Thread(target = send).start()
The error is at line 19 in the client code (where its receiving and printing any data sent by the server)
Any help would be greatly appreciated.
The most probable reason is the recursion in your send and receive routines, I changed them to be loops instead.
def recv():
while True:
data = s.recv(BUFFER_SIZE).decode()
if not data: break
print(data)
def send():
while True:
message = str(input())
if message != "/exit":
message = name + ": " + message
s.send(message.encode())
A solution to shutting down these threads is given here: Is there any way to kill a Thread in Python?
But it is not necessary to run send and receive in single threads in this scenario in the clients.
EDIT:
I read again carefully your code. In the client you start the send and receive method as threads. The send thread does not get any input for its message string in the thread and because you loop it, it sends empty messages to the server or (in my case) exits with an error.
I'm am trying to write a client program in Python that can send and receive from the same socket, but it is always giving me the same error which address is already in use. Here is the function I'm trying to write.
def Login():
username=raw_input()
password=raw_input()
message=raw_input()
array=[username,password,message]
TCP_IP = '127.0.0.1'
TCP_PORT = 5563
BUFFER_SIZE = 1024 # Normally 1024, but we want fast response
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((TCP_IP, TCP_PORT))
array_string=pickle.dumps(array)
sock.send(array_string)
sock.close()
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind((TCP_IP, TCP_PORT))
sock.listen(1)
conn, info = sock.accept()
while 1:
data = serverSocket.recv(1024)
if not data:break
conn.send(data)
conn.close()
There is a bunch of truly newbie errors here.
You can't ever connect a TCP socket to itself. There must be two different sockets.
If you really want to get the data you sent earlier at a listening socket, this listening socket must be created, bound and configured to listen before the client side connects (or, at least, in parallel to this connect attempt, in a few seconds, so the connect attempt will try - but this very likely won't work on localhost).
You can't wait on connect and on accept in the same thread if both are blocking. The simplest approach is to separate the client side and the server side to 2 different programs and run them manually in parallel. Then, after successful debugging, you will be able to do this in different threads of the same process, or using an event-driven engine.
While you may not be able to connect a socket to itself to send and receive data, you might be able to learn from the following example inspired by your code that attempts to do something similar.
import _thread
import pickle
import socket
import time
def main():
"""Run a server in a thread and start a client to talk to it."""
_thread.start_new_thread(run_server, ('', 5563))
run_client('localhost', 5563)
def run_server(host, port):
"""Handle all incoming connections by spawning worker threads."""
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind((host, port))
server.listen(5)
while True:
_thread.start_new_thread(handle_connection, server.accept())
def handle_connection(client, address):
"""Answer an incoming question from the connected client."""
print('Incoming connection from', address)
client.settimeout(0.1)
data = recvall(client)
client.shutdown(socket.SHUT_RD)
question = pickle.loads(data)
answer = '''len(username) = {}
len(password) = {}
len(message) = {}'''.format(*map(len, question))
client.sendall(answer.encode())
client.shutdown(socket.SHUT_WR)
client.close()
print('Finished with', address)
def recvall(connection):
"""Receive all data from a socket and return as a bytes object."""
buffer = bytearray()
while True:
try:
data = connection.recv(1 << 12)
except socket.timeout:
pass
else:
if data:
buffer.extend(data)
else:
return bytes(buffer)
def run_client(host, port):
"""Collect information from question and display returned answer."""
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
time.sleep(0.1) # wait for server to start listening for clients
client.connect((host, port))
time.sleep(0.1) # wait for handler thread to display connection
username = input('Username: ')
password = input('Password: ')
message = input('Message: ')
question = pickle.dumps((username, password, message))
client.sendall(question)
client.shutdown(socket.SHUT_WR)
answer = recvall(client)
client.shutdown(socket.SHUT_RD)
client.close()
print(answer.decode())
time.sleep(0.1) # wait for handler to cleanly terminate execution
if __name__ == '__main__':
main()