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POThreaded UDP Listener Function
 

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    <p>I'm pretty new to Python, so I apologize if my problem is amateurish. </p> <p>I'm trying to make a simple program that allows a user to see UDP messages that are being broadcast. In order for the program to not lock up, I of course need to create a separate thread to listen for the broadcast. </p> <p>Before I attempted to implement threading, the program worked great. It just waited for UDP messages and displayed them in the <code>TextView</code> when it received one. Of course, this locked up the main thread.</p> <p>Here is my code: (Yes, I know there are several irrelevant issues with my code, but please ignore them. e.g., I never close the <code>socket</code>. I will address these issues later.)</p> <pre><code>import socket import select import sys import threading try: import pygtk pygtk.require("2.0") except: pass try: import gtk except: print("GTK not available!") sys.exit(1) class GUI: def __init__(self): self.builder = gtk.Builder() self.builder.add_from_file("UDPListener.ui") dic = {"on_mainWindow_destroy" : self.quit, "on_listenButton_clicked" : self.startThread, "on_stopListenButton_clicked" : self.stopListening} self.builder.connect_signals(dic) self.listenerThread = threading.Thread(target = self.listen) def startThread(self, widget): self.listenerThread.start() def listen(self): bufferSize = 1024 IPAddress = "0.0.0.0" IPAddress: 0.0.0.0 portNumber = 50000 udpClient = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) textView = self.builder.get_object("messagesReceivedEntry").get_buffer() textView.text = textView.get_text(textView.get_start_iter(),textView.get_end_iter()) textView.set_text("Listening...") try: udpClient.bind((IPAddress, portNumber)) udpClient.setblocking(0) except: print "Cannot connect." try: while True: result = select.select([udpClient],[],[]) message = result[0][0].recv(bufferSize) print message except: print "Cannot receive message" def quit(self, widget): sys.exit(0) def stopListening(self, widget): pass gui = GUI() gtk.main() </code></pre> <p>The code will run and everything runs ok, but it never prints any messages (I broadcast them myself).</p> <hr> <p><strong>UPDATE:</strong></p> <p>Thanks to J.F. Sebastian's answer, I altered my code to include the following:</p> <pre><code>import socket import select import sys import threading import gobject try: import pygtk pygtk.require("2.0") except: pass try: import gtk except: print("GTK not available!") sys.exit(1) gobject.threads_init() class GUI: def __init__(self, UDPClient): self.udpClient = UDPClient self.builder = gtk.Builder() self.builder.add_from_file("TestUDPListenerREORG.ui") dic = {"on_mainWindow_destroy" : self.quit, "on_listenButton_clicked" : self.startThread, "on_stopListenButton_clicked" : self.stopListening} self.builder.connect_signals(dic) self.textView = self.builder.get_object("messagesReceivedEntry").get_buffer() self.textViewText = self.textView.get_text(self.textView.get_start_iter(),self.textView.get_end_iter()) self.listening = False self.listenerThread = threading.Thread(target = self.listen) def startThread(self, widget): self.listenerThread.start() pass def listen(self): try: self.udpClient.connect() except: print "Cannot connect." try: while True: result = select.select([self.udpClient.client],[],[]) message = result[0][0].recv(1024) print message gobject.idle_add(self.updateGUI, message) except: print "Cannot receive message" def updateGUI(self, message): print "updating..." self.textView.set_text(self.textViewText + "\n" + message) print message def quit(self, widget): self.udpClient.close() sys.exit(0) def stopListening(self, widget): pass class UDPClient: def __init__(self, IPAddress, portNumber): self.IPAddress = IPAddress self.portNumber = portNumber self.bufferSize = 1024 self.client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) def connect(self): try: self.client.bind((self.IPAddress, self.portNumber)) self.client.setblocking(0) except: print "Cannot connect." def close(self): try: self.client.close() except: pass udpClient = UDPClient("0.0.0.0", 50000) gui = GUI(udpClient) gtk.main() </code></pre> <p>So far everything runs perfectly. </p>
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