I am trying to run a function in the background, whilst continuing with said code in python.
The function I want to run in the background is from socket. Looking for specific data to cut the program off.
Here is the function:
def receive():
host = ""
port = 13000
buf = 1024
addr = (host,port)
Sock = socket(AF_INET, SOCK_DGRAM)
Sock.bind(addr)
(data, addr) = Sock.recvfrom(buf)
return data
Here is the code I want to run:
while True:
r = receive()
if r == "stop":
break
#Cannot get past here, because of the function running.
#Should loop over and over, until stop data is received
print "Running program"
I have tried threading, with r = threading.Thread(target=receive()) with no joy.
Rookie error:
r = threading.Thread(target=receive())
I did not take the brackets off the receive():
r = threading.Thread(target=receive)
You can't return to the invoking thread from an invoked thread's target function. Instead, you need some inter-thread communication system. Below, is an example using Python's Queue to pass received datagrams between the two threads. I've used a threading.Event to signal when the receiver thread should stop.
#!/usr/bin/env python
import socket
import threading
from queue import Empty, Queue
class DatagramReceiver(threading.Thread):
def __init__(self, stop, queue):
super().__init__()
self._stop = stop
self._queue = queue
def run(self):
with socket.socket(AF_INET, SOCK_DGRAM) as sock:
sock.bind(('', 13000))
while not self._stop.is_set():
data = sock.recvfrom(1024)[0]
if data == 'stop':
self._stop.set()
break
self._queue.put(data)
def main():
stop = threading.Event()
queue = Queue()
reader = DatagramReceiver(stop, queue)
reader.deamon = True
reader.start()
while not stop.is_set():
user_input = input('Press RETURN to print datagrams, or q quit')
if user_input == 'q':
break
while True:
try:
datagram = queue.get_nowait()
except Empty:
break
print(datagram)
stop.set()
reader.join()
Related
my script works like this:
# other part of code
class request(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
def run(self):
while True:
try:
socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
socket.connect((host), (port))
socket.send(str.encode("test"))
except:
socket.close()
def loop():
for x in range(5):
request(x).start()
# other
# part
# of code
def startall():
# some other code
choice = input("command: ")
if choice == "request":
loop()
elif choice == "stop":
# ?
# some other code
startall()
Is there a way to stop sending request if the input is "stop"? Note that this is just a sample, my script doesn't work like this. I put this code just to let you understand what is my problem
If you want to stop all requests at once you can modify your class as folows:
class request(threading.Thread):
REQUESTS_ALLOWED = True
def run(self):
while request.REQUESTS_ALLOWED:
socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
socket.connect((host), (port))
socket.send(str.encode("test"))
except:
pass # Do what you need
finally:
socket.close()
Notice the alternation of closing socket. In your code the socket was closed when garbage collector destroyed your variable socket. With my alternation it's guaranteed that socket is closed with every iteration.
The start and stop events now can change the state of all request objects.
if choice == "request":
request.REQUESTS_ALLOWED = True
loop()
elif choice == "stop":
request.REQUESTS_ALLOWED = False
After setting REQUESTS_ALLOWED to False you should join() all running threads. It's just recommendation (and you don't have to do it) because normally when function returns it indicates that something is done. So after return from function startall() with choice = "stop" I would expect that all started threads are stopped.
Full code example:
import threading
import time
class Request(threading.Thread):
REQUESTS_ALLOWED = True
active_threads = set()
def __init__(self):
threading.Thread.__init__(self)
def start(self):
Request.active_threads.add(self) # Add thread to set for later use
super().start()
def run(self):
while Request.REQUESTS_ALLOWED:
print("Thread {} is alive.".format(self.name))
time.sleep(1)
print("Thread {} is done.".format(self.name))
def loop():
for x in range(5):
Request().start()
def startall(choice):
if choice == "request":
Request.REQUESTS_ALLOWED = True
loop()
elif choice == "stop":
Request.REQUESTS_ALLOWED = False
# Iterate through active threads and wait for them
for thread in Request.active_threads:
thread.join()
Request.active_threads.clear()
startall("request")
time.sleep(3)
startall("stop")
The code was tested in Python 3.6.1
From my understanding python can only run 1 thread at a time so if I were to do something like this
import socket, select
from threading import Thread
import config
class Source(Thread):
def __init__(self):
self._wait = False
self._host = (config.HOST, config.PORT + 1)
self._socket = socket.socket()
self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self._sock = None
self._connections = []
self._mount = "None"
self._writers = []
self._createServer()
Thread.__init__(self)
def _createServer(self):
self._socket.bind(self._host)
self._socket.listen(2)
self._connections.append(self._socket)
self._audioPackets=[]
def _addPacket(self, packet):
self._audioPackets.append(packet)
def _removePacket(self, packet):
self._audioPackets.remove(packet)
def _getPacket(self):
if len(self._audioPackets) > 0:
return self._audioPackets[0]
else:
return None
def _sendOK(self, sock):
sock.send("OK")
def _sendDenied(self, sock):
sock.send("DENIED")
def _sendMount(self, sock):
sock.send("mount:{0}".format(self._mount))
def _sendBufPacket(self, sock, packet):
packet = "buffer:%s" % packet
sock.send(packet)
def recv(self, sock, data):
data = data.split(":", 1)
if data[0] == "WAIT": self._wait = True
elif data[0] == "STOP_WAITING": self._wait = False
elif data[0] == "LOGIN":
if data[1] == config.SOURCE_AUTH:
self._source = sock
self._sendOK(sock)
else:
self._sendClose(sock)
elif data[0] == "MOUNT":
if self._source == sock:
self._mount = data[1]
else:
self._sendClose(sock)
elif data[0] == "CLIENT":
self._sendMount(sock)
self._writers.append(sock)
def _sendCloseAll(self):
for sock in self._connections:
sock.send("CLOSE")
sock.close()
def _sendClose(self, sock):
sock.send("CLOSE")
sock.close()
def main(self):
while True:
rl, wl, xl = select.select(self._connections, self._writers, [], 0.2)
for sock in rl:
if sock == self._socket:
con, ip = sock.accept()
self._connections.append(con)
else:
data = sock.recv(config.BUFFER)
if data:
self.recv(sock, data)
else:
if sock in self._writers:
self._writers.remove(sock)
if sock in self._connections:
self._connections.remove(sock)
for sock in wl:
packet = self._getPacket()
if packet != None:
self._sendBufPacket(sock, packet)
def run(self):
self.main()
class writeThread(Thread):
def __init__(self):
self.running = False
def make(self, client):
self.client = client
self.running = True
def run(self):
host = (config.HOST, config.PORT+1)
sock = socket.socket()
sock.connect(host)
sock.send("CLIENT")
sock.send("MOUNT:mountpoint")
while self.running:
data = sock.recv(config.BUFFER)
if data:
data = data.split(":", 1)
if data[0] == "buffer":
self.client.send(data[1])
elif data[0] == "CLOSE":
self.client.close()
break
if __name__=="__main__":
source = Source()
source.start()
webserver = WebServer()
webserver.runloop()
if I need to build the webserver part I will. But, I'll explain it.
Okay, so basically when someone connects to the websever under the mountpoint that was set, They will get there own personal thread that then grabs the data from Source() and sends it to them. Now say another person connects to the mount point and the last client as well as the source is still going. Wouldn't the new client be blocked from getting the Source data considering there are two active threads?
Your understanding of how Threads work in Python seems to be incorrect, based on the question you are asking. If used correctly, threads will not be blocking: you can instantiate multiple thread with Python. The limitation is that, due to the Global Interpreter Lock (GIL), you cannot get the full parallelism expected in thread programming (e.g. simultaneous execution and thus, reduced runtime).
What is going to happen in your case is that the two threads will take, together, the same amount of time that they would take if they were executed sequentially (although that is not necessarily what happens in practice).
Okay, I have copy and pasted some Python3 code that I have already written for a project that I am currently working on. With modification, you can make this code serve your purposes.
The code uses multiprocessing and multithreading. For my purposes, I am using multiprocessing so that sockets will run on one processor, and I can run a GUI program on another processor. You can remove the multiprocessor part if you prefer. The code below runs a socket message server. The server will listen for clients one at a time. Once a client has connected, a new thread will be initiated to handle all the communications between the server and each client. The server will then continue to search for for clients. At the moment however, the server only listens to data being sent from each client, and then it prints it to the terminal. With a small amount of effort, you can modify my code to send information from the server to each client individually.
import multiprocessing
import threading
from threading import Thread
class ThreadedServer(object):
def __init__(self, host, port):
self.host = host
self.port = port
self.sock = socket(AF_INET, SOCK_STREAM)
self.sock.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
self.sock.bind((self.host, self.port))
def listen(self):
self.sock.listen(3) #Allow 3 Clients to connect to this server
while True:
#The program will search for one client at a time
print("Searching for Client")
client, address = self.sock.accept()
print(address, " is connected")
#client.settimeout(60)
#Once a client has been found, start a individual client thread
d = threading.Thread(target = self.listenToClient, args=(client, address))
d.daemon = True
d.start()
def listenToClient(self, client, address):
size = 1024
while True:
try:
data = client.recv(size)
if not data:
break
if data:
print(data)
#client.send(response)
else:
raise error('Client disconnected')
except:
client.close()
return False
def dataSharingHost():
#Using Sockets to send information between Processes
#This is the server Function
#ThreadServer(Host_IP, Port_Number), for LocalHost use ''
ThreadedServer('', 8000).listen()
def Main():
commServer = multiprocessing.Process(target=dataSharingHost, args=())
commServer.daemon = True
commServer.start()
if __name__== '__main__':
Main()
And to be fair, my code is modified from https://www.youtube.com/watch?v=qELZAi4yra8 . The client code is covered in those videos. I think the 3rd video covers the multiple client connects.
I wrote a udp no echo server in my program, I used thread to running and listen some message send by others. But it seems I couldn't stop it use tl.stop(), when I input q or quit. Some of my code is following:
class treadListen(threading.Thread):
def __init__(self):
self.running = True
threading.Thread.__init__(self)
def run(self):
address = ('localhost', 16666)
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(address)
while True:
data = sock.recv(65535)
print "MESSAGE:{0}".format(data)
sock.close()
def stop(self):
self.running = False
# end of class thread_clock
if __name__ == "__main__":
tl = treadListen()
tl.start()
while True:
message = raw_input("CMD>")
if not message:
print "Please input command!"
continue
elif (message == 'quit') or (message == 'q'):
tl.stop()
break
else:
print "input is {0}".format(message)
# do something
continue
print "[CONNECTION CLOSED!]"
I was trying to add sock.shutdown(socket.SHUT_RDWR) and sock.close() to def stop of class, but it doesn't work.
How can I stop the thread safety? Thanks!
Your while loop while True: works forever, so I guess your close or shutdown calls to the socket never can gets in way to work.
You should change while True: to while self.running: and that should do the trick.
Thanks ntki,rbp,st.
The problem solved use following code:
class treadListen(threading.Thread):
def __init__(self):
**self.running = True**
threading.Thread.__init__(self)
def run(self):
address = ('localhost', 16666)
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
**sock.settimeout(1)**
sock.bind(address)
**while self.running:
try:
data = sock.recv(65535)
print "MESSAGE:{0}".format(data)
except Exception, e:
continue**
sock.close()
def stop(self):
**self.running = False**
# end of class thread_clock
I'm running a python server using the socketserver module in python 2.7. OmniPeek packet analysis tool shows the TCP handshake completes,
but the server immediately sends a reset packet killing the connection.
Simplified server code which shows the problem is:
from threading import Lock, Thread, Condition
import SocketServer
import socket
import sys
import time
class ThreadedTCPRequestHandler(SocketServer.BaseRequestHandler):
def __init__(self, state, *args, **keys):
try:
state['lock'].acquire()
state['client_count'] += 1
finally:
state['lock'].release()
self.state = state
SocketServer.BaseRequestHandler.__init__(self, *args, **keys)
def handle(self):
self.state['lock'].acquire()
count = self.state['client_count']
self.state['lock'].release()
while True:
try:
self.state['lock'].acquire()
running = self.state['running']
self.state['lock'].release()
if not running:
break;
time.sleep(1) # do some work
except Exception as msg:
print msg
print "ThreadedTCPRequestHandler shutting down..."
class ThreadedTCPServer(SocketServer.ThreadingMixIn, SocketServer.TCPServer):
pass
def handler_factory(state):
def createHandler(*args, **keys):
return ThreadedTCPRequestHandler(state, *args, **keys)
return createHandler
if __name__ == "__main__":
lock = Lock()
cv = Condition(lock)
state = {'running': True, 'client_count': 0, 'lock': lock, 'cv': cv}
server = ThreadedTCPServer(('localhost', 12345), handler_factory(state))
server_thread = Thread(target=server.serve_forever)
server_thread.daemon = True
server_thread.start()
print "Server loop running in thread:", server_thread.name
# wait for a client to connect
cv.acquire()
while state['client_count'] == 0 and state['running']:
cv.wait(1.0)
# print msg
cv.release()
# substitute real work here...
time.sleep(5)
lock.acquire()
state['running'] = False
lock.release()
server.shutdown()
and the client code:
import socket
if __name__ == "__main__":
try:
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'ip: {} port {}'.format('10.4.2.54', 12345)
client.connect(('10.4.2.54', 12345))
while True:
data = client.recv(4096)
if len(data) == 0:
break;
print 'data: {}'.format(data)
client.shutdown(socket.SHUT_RDWR)
client.close()
except Exception as msg:
print msg
The server code is based off python 2.7 docs serversocket Mixin example, and seems pretty straightforward, but...
Thanks
not sure what your expected behaviour is but if you make a couple of changes, you'll be able to see that it can work
replace your handle method
def handle(self):
while True:
try:
data = self.request.recv(1024).strip()
if len(data) != 0:
print data
time.sleep(1) # do some work
self.request.send('test data')
except Exception as msg:
print msg
break
print "ThreadedTCPRequestHandler shutting down..."
and client(inside main):
try:
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'ip: {} port {}'.format('localhost', 1232)
client.connect(('localhost', 1232))
client.send('test')
n = 0
while True:
data = client.recv(4096)
if len(data) != 0:
print 'data: {}'.format(data)
time.sleep(1)
n += 1
client.send('keep-alive' + str(n) + '\n')
print 'here'
client.shutdown(socket.SHUT_RDWR)
client.close()
except Exception as msg:
print msg
I just modded it to send stuff and print stuff. But it doesn't crash.
I think there is an issue with your self.state['lock'].acquire() and release() calls. I took out the 'running' check as it's not really used except at the end of the server code.
Also, without any action, sockets will time out.
Once again, I'm not claiming to have 'fixed' your problem...and I'm not sure exactly what you are looking for...just helping you brainstorm!
Apologies - red herring. The problem is only occurring under VM when server is running under guest and client is running under host. TCP reset packet never sent when both client and server are running either on host or guest
I want to read messages from either a Queue.Queue or a TCP socket, whichever comes first.
How can it be achieved without resorting to 2 threads ?
Platform is CPython 2.7.5 on Windows
There is a very nice trick to do this here that applies to your problem.
import queue
import socket
import os
class PollableQueue(queue.Queue):
def __init__(self):
super().__init__()
# Create a pair of connected sockets
if os.name == 'posix':
self._putsocket, self._getsocket = socket.socketpair()
else:
# Compatibility on non-POSIX systems
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('127.0.0.1', 0))
server.listen(1)
self._putsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self._putsocket.connect(server.getsockname())
self._getsocket, _ = server.accept()
server.close()
def fileno(self):
return self._getsocket.fileno()
def put(self, item):
super().put(item)
self._putsocket.send(b'x')
def get(self):
self._getsocket.recv(1)
return super().get()
To do it in a single thread, you'll have to use non-blocking methods, and merge them into a single event loop. I'm actually using select instead of non-blocking socket I/O here, since it's slightly cleaner if you need to read from multiple sockets...
import socket
import select
import Queue
import time
TIMEOUT = 0.1 # 100ms
def process_queue_item(item):
print 'Got queue item: %r' % item
def process_socket_data(data):
print 'Got socket data: %r' % data
def main():
# Build queue
queue = Queue.Queue()
for i in range(10):
queue.put(i)
queue.put(None) # Using None to indicate no more data on queue
queue_active = True
# Build socket
sock = socket.socket()
sock.connect(('www.google.com', 80))
sock.send('GET / HTTP/1.0\r\n\r\n')
socket_active = True
# Main event loop
while 1:
# If there's nothing to read, bail out
if not (socket_active or queue_active):
break
# By default, sleep at the end of the loop
do_sleep = True
# Get data from socket without blocking if possible
if socket_active:
r, w, x = select.select([sock], [], [], TIMEOUT)
if r:
data = sock.recv(64)
if not data: # Hit EOF
socket_active = False
else:
do_sleep = False
process_socket_data(data)
# Get item from queue without blocking if possible
if queue_active:
try:
item = queue.get_nowait()
if item is None: # Hit end of queue
queue_active = False
else:
do_sleep = False
process_queue_item(item)
except Queue.Empty:
pass
# If we didn't get anything on this loop, sleep for a bit so we
# don't max out CPU time
if do_sleep:
time.sleep(TIMEOUT)
if __name__ == '__main__':
main()
Output looks like...
Got socket data: 'HTTP/1.0 302 Found\r\nLocation: http://www.google.co.uk/\r\nCache-Co'
Got queue item: 0
Got socket data: 'ntrol: private\r\nContent-Type: text/html; charset=UTF-8\r\nSet-Cook'
Got queue item: 1
Got socket data: 'ie: PREF=ID=a192ab09b4c13176:FF=0:TM=1373055330:LM=1373055330:S='
Got queue item: 2
etc.
You can do something along these lines:
def check_for_message(queue,socket,sock_accept_size=512):
socket.setblocking(0)
while True:
try:
sock_msg=socket.recv(sock_accept_size)
except socket.error:
"""Do stuff if there is no message"""
sock_msg=None
try:
que_msg=queue.get()
except Queue.Empty:
"""Do stuff if there is no message"""
que_msg=None
yield (que_msg,sock_msg)
Then you can iterate through it using:
for que_message,sock_message in check_for_message(que_instance,socket_instance):
print que_message,sock_message