In python, you can define maximum number of socket connections by parameter of listen() function... for example:
serversocket = socket.socket(
socket.AF_INET, socket.SOCK_STREAM)
serversocket.bind((socket.gethostname(), 80))
serversocket.listen(1) // allow only 1 connection
But the problem is that when second client wants to connect, connection is being refused. And I would like to disconnect the old user and connect the new one. Could anybody help me with that?
Probably an answer:
I am posting it in question as it is probable answer (I didn't have time to check it)
serversocket = socket.socket(
socket.AF_INET, socket.SOCK_STREAM)
serversocket.bind((socket.gethostname(), 80))
serversocket.listen(10) // allow 10 connections, but disconnect previous later
someone_connected = 0
while 1:
(clientsocket, address) = serversocket.accept()
if(someone_connected) someone_connected.close()
someone_connected = clientsocket
I am not sure that I fully understand you question, but I think the following example can meet your requirement. the server can disconnect the old user and serve the new one.
the sever side:
#!/usr/bin/env python
import socket
import multiprocessing
HOST = '127.0.0.1'
PORT = 50007
# you can do your real staff in handler
def handler(conn, addr):
try:
print 'processing...'
while 1:
data = conn.recv(1024)
if not data:
break
print data
conn.sendall(data)
conn.close()
print 'processing done'
except:
pass
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(5)
processes = []
while True:
conn, addr = s.accept()
print conn, addr
[p.terminate() for p in processes] # to disconnect the old connection
# start process newer connection and save it for next kill
p = multiprocessing.Process(target=handler, args=(conn, addr))
processes = [p]
p.start()
newest_conn = conn # this is the newest connection object, if you need it
For test, the client side:
#!/usr/bin/env python
import socket
import time
import multiprocessing
HOST = '127.0.0.1'
PORT = 50007
def client():
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
time.sleep(0.1)
try:
for n in range(20):
s.send(str(n))
data = s.recv(1024)
print data
time.sleep(0.5)
s.send('')
s.close()
except:
pass
if __name__ == "__main__":
for i in range(5):
print 'user %i connect' %i
p = multiprocessing.Process(target=client)
p.start() # simulate a new user start connect
time.sleep(3)
Try it :-)
You have a wrong assumption built into your question - the single argument to socket listen() is not the "number of connections", but a backlog - number of pending, but not yet accepted client connections the kernel holds for you for a while.
Your problem then seems to be that you have accepted one connection, and reading/writing to it in a loop, and not calling accept() again. The kernel holds the request for any new client connection for some timeout, then notifies the client that the server is not accepting it.
You want to look into select() functionality, as suggested in the comments.
Related
I'm creating a program that uses threads to handle sockets and input at the same time. I've narrowed down the errors I'm getting to be replicable in these couple dozen lines of code. What happens to anyone else who runs the code below? I encounter a hang-up in waiting for the recv in the client. If I further try to send() more data in the server, I get a Broken Pipe error. And, even more weirdly, if I comment out the line that calls input(), the sockets work just fine.
What kind of weird interaction is going on between input(), sockets, and threading? And does anyone have a solution to this? Here's some code that generates the error.
Server:
import socket
import threading
def handle_connection(conn, addr):
data = conn.recv(1024)
message = data.decode('ascii').split()
s = "TEST"
conn.send(bytes(s, 'ascii')) #
conn.close()
def handle_input():
while True:
s = input()
print(s)
HOST = "127.0.0.1" # The server's hostname or IP address
PORT = 2000 # The port used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT)); #Empty first string = INADDR_ANY
s.listen();
w = threading.Thread(target=handle_input)
w.start()
while True:
conn, addr = s.accept()
x = threading.Thread(target=handle_connection, args=(conn, addr))
x.start()
s.close()
Client:
import socket
HOST = "127.0.0.1" # The server's hostname or IP address
PORT = 2000 # The port used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
message = "find_successor a"
s.connect((HOST, PORT))
s.sendall(bytes(message, 'ascii'))
data = s.recv(1024)
print(f"Received {data!r}")
I appreciate any help or insight!
I want to set up a simple echo server that just echoes back whatever the client sends to it. However, currently the server disconnects (the server socket closes) after it echoes back the first client message. I want to be able to "chat" continuously with the server, where the server just echoes back several consecutive messages I send without disconnecting; e.g.:
"Hi there!"
"Echoing: Hi there!"
"How are you?"
"Echoing: How are you?"
"Cheers!"
"Echoing: Cheers!"
etc.
Currently I have the following code:
server.py:
import socket
HOST = '127.0.0.1'
PORT = 5000
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen()
conn, addr = s.accept()
with conn:
while True:
data = conn.recv(1024)
if not data:
break
conn.sendall(data)
client.py:
import socket
HOST = '127.0.0.1'
PORT = 5000
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
data = s.recv(1024)
print('Echoing: ', repr(data))
The server, however, disconnects after it echoes back the first client message (probably because of the if not data: break statement).
P.S. I'd appreciate any additional explanations which might be necessary - this example has educational purposes, so I'm not (only) after getting the code running.
Thanks!
server.py:
import socket
HOST = '127.0.0.1'
PORT = 5000
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen()
conn, addr = s.accept()
with conn:
while True:
data = conn.recv(1024)
if data.decode() == "bye":
break
conn.sendall(data)
conn, addr = s.accept()
I will show you the code I created then talk you through it:
Server:
import socket
HOST = '127.0.0.1'
PORT = 5000
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen()
conn, addr = s.accept()
with conn:
while True:
data = conn.recv(1024)
conn.sendall(data)
For the server I removed:
if not data:
break
It simply wasn't working for me. If you know your message is going to be less than the 1024 bytes( which here it is) it's unnecessary. But if you want a longer message change that value to a bigger number to accommodate. So yes you were right in suspecting it was that line.
Client:
import socket
HOST = '127.0.0.1'
PORT = 5000
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.connect((HOST, PORT))
print("Connected")
while True:
print("Sending data")
s.sendall(b'Hello, world')
print("Recieving data")
data = s.recv(1024)
print('Echoing: ', repr(data))
For the client side I just added the send and receive process into a loop.
Things to note:
This only works for me when run through the terminal, I don't know if you know how to do that so sorry if you do, here's a link explaining:
https://www.wikihow.com/Use-Windows-Command-Prompt-to-Run-a-Python-File
I assumed you use Windows.
You will need to follow the process for both your client.py programme and server.py programme. Make sure you run the server.py programme first.
This will cause an infinite loop of sending and receiving. Press Ctrl+C to terminate.
I hope this solves your problem and you can edit the code accordingly. Any further problems please do comment and I'll try to get back to you.
Maybe use sleep instead of break
if not data:
time.sleep(1)
continue
You have to import time module for this.
I have started to make my own TCP server and client. I was able to get the server and the client to connect over my LAN network. But when I try to have another client connect to make a three way connection, it does not work. What will happen is only when the first connected client has terminated the connection between, the server and the client, can the other client connect and start the chat session. I do not understand why this happens. I have tried threading, loops, and everything else I can think of. I would appreciate any advice. I feel like there is just one small thing i am missing and I can not figure out what it is.
Here is my server:
import socket
from threading import Thread
def whatBeip():
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.connect(('8.8.8.8', 0))
local_ip_address = s.getsockname()[0]
print('Current Local ip: ' + str(local_ip_address))
def clietConnect():
conn, addr = s.accept()
print 'Connection address:', addr
i = True
while i == True:
data = conn.recv(BUFFER_SIZE)
if not data:
break
print('IM Recieved: ' + data)
conn.sendall(data) # echo
whatBeip()
TCP_IP = ''
TCP_PORT = 5005
BUFFER_SIZE = 1024
peopleIn = 4
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP, TCP_PORT))
s.listen(peopleIn)
for client in range(peopleIn):
Thread(target=clietConnect()).start()
conn.close()
Here is my client
import socket
TCP_IP = '10.255.255.3'
TCP_PORT = 5005
BUFFER_SIZE = 1024
MESSAGE = "Hello, World!"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
i = True
while i == True:
s.sendall(raw_input('Type IM: '))
data = s.recv(BUFFER_SIZE)
s.close()
This is your main problem: Thread(target=clietConnect()).start() executes the function clientConnect and uses it's return value as the Thread function (which is None, so the Thread does nothing)
Also have a look at:
1) You should wait for all connections to close instead of conn.close() in the end of the server:
threads = list()
for client in range(peopleIn):
t = Thread(target=clietConnect)
t.start()
threads.append(t)
for t in threads: t.join()
and to close the connection when no data is received:
if not data:
conn.close()
return
2) You probably want to use SO_REUSEADDR [ Socket options SO_REUSEADDR and SO_REUSEPORT, how do they differ? Do they mean the same across all major operating systems? , Python: Binding Socket: "Address already in use" ]
3) And have a look at asyncio for python
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()
Why does my connection stop after 3 print statements if I have the conn.send() line? If that line is commented out, the connection stays open indefinitely. It is hitting the exception for some reason, but I don't know why and I am inexperienced with python.
server.py:
import random
import signal
import socket
import struct
import sys
import time
PORT = 1234
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(('', PORT))
s.listen(1)
print("Server started on port %u" % PORT)
try:
while True:
(conn, addr) = s.accept()
conn.setblocking(0)
print("Client connected: %s:%d" % addr)
while True:
print "hey"
conn.send("random")
time.sleep(1)
except:
s.close()
print "exception"
client.py:
import socket # Import socket module
s = socket.socket() # Create a socket object
host = socket.gethostname() # Get local machine name
port = 1234 # Reserve a port for your service.
s.connect((host, port))
print s.recv(1024)
s.close
The reason for this behavior is the socket is actually closed after the clients first recv(), your server just doesn't realize it until the third attempt at send(). Calling close() in your client didn't change anything because previously the program was terminating which closed the socket anyway. This thread explains why this is very likely what's happening. To test this theory, you could try having the client sleep (or select) and print more recv() calls, before closing the socket.