asyncore asynchat

Discussion in 'Python' started by Michael Welsh, Jul 15, 2003.

  1. In order to learn sockets in Python I am trying to write a simple group chat
    server and client. I need a little nudge, please. My question contains some
    GUI but only as decoration. The root question is asyncore / asynchat. I
    have read that twisted makes this all simple, but, I wanted to get my hands
    dirty here for educational purposes.

    I've managed to build a small echo server with asyncore and asynchat that can
    handle any number of connections and repeat to all clients what was sent in
    by individual clients. The server seems to work well.

    The GUI client, wxPython, creates a socket on open. The user types some text
    and clicks [SEND]. The send event puts the text out to the socket then reads
    the response and adds it to list control. Everything works well.

    I'm now ready for the next step, to disconnect the send data from the recieve
    data. So a user who does not send text, still gets what others may have
    written. I need to somehow poll the thread so "add to list control" can be
    triggered on recieving the data.

    I've tried several approaches and can't seem to get it right. First I tried
    setting up a separate threading.Thread that created the socket. This way I
    could put a poll on the socket. I even created (borrowed) a custom event so
    when data was found, it could notify the GUI and call the "add to list
    control" But I must have been doing it wrong because it kept locking up in
    the loop..

    I knew from the server side that asynchat has built in helpers with
    collect_incoming_data() and found_terminator(). (my terminator is appended
    when data is sent to the server) I could then use the asyncore.poll() in my
    threading.Thread to raise the custom event that sends data to the GUI, when
    something comes over the socket.

    I think I have the concepts right, but the execution breaks down here. I
    tried having the threading.Thread create an asyn_chat but I keep getting
    errors that I assume the asyncore.dispatcher takes care of. So... maybe I
    should use both core and chat on the client as well as the server. The only
    examples of dispatcher I can find open up an asyn_chat on "listen". The
    client needs to initiate the communication when it starts. The server is
    listening and will respond. I won't know on which port the response will
    come back.

    Here's some bits showing what I'm trying to do. You may find some of it
    familiar. I hope I didn't clip anything that may have been needed If anybody
    has time to point out where I'm going wrong it would be very helpful. Thank
    you if you were patient enough to get this far...

    import threading
    import time
    import socket
    import asyncore
    import asynchat
    from wxPython.wx import *

    # server is listening on ...
    REMOTE_HOST = '172.0.0.1'
    REMOTE_PORT = 50001

    class MyTest(wxFrame):
    def __init__(self, parent, ID, title):
    # Initialize wxFrame
    wxFrame.__init__(self, .....

    # start the thread
    self.network = NetworkThread(self)
    self.network.start()
    EVT_NETWORK(self,self.OnNetwork)

    # build rest of GUI... works fine


    # the network thread communicates back to the main
    # GUI thread via this sythetic event
    class NetworkEvent(wxPyEvent):
    def __init__(self,msg=""):
    wxPyEvent.__init__(self)
    self.SetEventType(wxEVT_NETWORK)
    self.msg = msg

    wxEVT_NETWORK = 2000
    def EVT_NETWORK(win, func):
    win.Connect(-1, -1, wxEVT_NETWORK, func)

    class NetworkThread(threading.Thread):
    def __init__(self,win):
    threading.Thread.__init__(self)
    self.win = win
    self.keep_going = true
    self.running = false
    self.MySock = NetworkServer(REMOTE_HOST, REMOTE_PORT,
    self.received_a_line)
    self.event_loop = EventLoop()

    def push(self,msg):
    self.MySock.push(msg)
    def is_running(self):
    return self.running
    def stop(self):
    self.keep_going = 0
    def check_status(self,el,time):
    if not self.keep_going:
    asyncore.close_all()
    else:
    self.event_loop.schedule(1,self.check_status)
    def received_a_line(self,m):
    self.send_event(m)
    def run(self):
    self.running = true
    self.event_loop.schedule(1,self.check_status)
    # loop here checking every 0.5 seconds for shutdowns etc..
    self.event_loop.go(0.5)
    # server has shutdown
    self.send_event("Closed down network")
    time.sleep(1)
    self.running = false

    # send a synthetic event back to our GUI thread
    def send_event(self,m):
    evt = NetworkEvent(m)
    wxPostEvent(self.win,evt)
    del evt

    class NetworkServer (asyncore.dispatcher):
    def __init__ (self, host, port, handler=None):
    asyncore.dispatcher.__init__(self)
    self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
    self.connect((host, port))

    def handle_connect (self):
    # I thought, maybe, the server would trigger this... nope
    ChatSocket (host, port, self.handler)

    def handle_read (self):
    data = self.recv (8192)
    self.send_event(self.data)
    print data

    def writable (self):
    return (len(self.buffer) > 0)

    def handle_write (self):
    sent = self.send (self.buffer)
    self.buffer = self.buffer[sent:]

    # send a synthetic event back to our GUI thread
    def send_event(self,m):
    evt = NetworkEvent(m)
    wxPostEvent(self.win,evt)
    del evt

    class ChatSocket(asynchat.async_chat):
    def __init__(self, host, port, handler=None):
    asynchat.async_chat.__init__ (self, port)

    def collect_incoming_data(self, data):
    self.data.append(data)

    def found_terminator(self):
    if self.handler:
    self.send_event(self.data)
    else:
    print 'warning: unhandled message: ', self.data
    self.data = ''

    class EventLoop:
    socket_map = asyncore.socket_map
    def __init__ (self):
    self.events = {}

    def go (self, timeout=5.0):
    events = self.events
    while self.socket_map:
    print 'inner-loop'
    now = int(time.time())
    for k,v in events.items():
    if now >= k:
    v (self, now)
    del events[k]
    asyncore.poll (timeout)

    def schedule (self, delta, callback):
    now = int (time.time())
    self.events[now + delta] = callback

    def unschedule (self, callback, all=1):
    "unschedule a callback"
    for k,v in self.events:
    if v is callback:
    del self.events[k]
    if not all:
    break

    # -----------------------------------------
    # Run App
    # -------------------------------------------
    class TestApp(wxApp):
    def OnInit(self):
    frame = MyTest(None, -1, "Test APP")
    frame.Show(true)
    self.SetTopWindow(frame)
    return true

    app = TestApp(0)
    app.MainLoop()
     
    Michael Welsh, Jul 15, 2003
    #1
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