Can I avoid a threaded UDP socket in Python dropping data?
- by 666craig
First off, I'm new to Python and learning on the job, so be gentle!
I'm trying to write a threaded Python app for Windows that reads data from a UDP socket (thread-1), writes it to file (thread-2), and displays the live data (thread-3) to a widget (gtk.Image using a gtk.gdk.pixbuf). I'm using queues for communicating data between threads.
My problem is that if I start only threads 1 and 3 (so skip the file writing for now), it seems that I lose some data after the first few samples. After this drop it looks fine. Even by letting thread 1 complete before running thread 3, this apparent drop is still there.
Apologies for the length of code snippet (I've removed the thread that writes to file), but I felt removing code would just prompt questions. Hope someone can shed some light :-)
import socket
import threading
import Queue
import numpy
import gtk
gtk.gdk.threads_init()
import gtk.glade
import pygtk
class readFromUDPSocket(threading.Thread):
def __init__(self, socketUDP, readDataQueue, packetSize, numScans):
threading.Thread.__init__(self)
self.socketUDP = socketUDP
self.readDataQueue = readDataQueue
self.packetSize = packetSize
self.numScans = numScans
def run(self):
for scan in range(1, self.numScans + 1):
buffer = self.socketUDP.recv(self.packetSize)
self.readDataQueue.put(buffer)
self.socketUDP.close()
print 'myServer finished!'
class displayWithGTK(threading.Thread):
def __init__(self, displayDataQueue, image, viewArea):
threading.Thread.__init__(self)
self.displayDataQueue = displayDataQueue
self.image = image
self.viewWidth = viewArea[0]
self.viewHeight = viewArea[1]
self.displayData = numpy.zeros((self.viewHeight, self.viewWidth, 3), dtype=numpy.uint16)
def run(self):
scan = 0
try:
while True:
if not scan % self.viewWidth: scan = 0
buffer = self.displayDataQueue.get(timeout=0.1)
self.displayData[:, scan, 0] = numpy.fromstring(buffer, dtype=numpy.uint16)
self.displayData[:, scan, 1] = numpy.fromstring(buffer, dtype=numpy.uint16)
self.displayData[:, scan, 2] = numpy.fromstring(buffer, dtype=numpy.uint16)
gtk.gdk.threads_enter()
self.myPixbuf = gtk.gdk.pixbuf_new_from_data(self.displayData.tostring(), gtk.gdk.COLORSPACE_RGB,
False, 8, self.viewWidth, self.viewHeight, self.viewWidth * 3)
self.image.set_from_pixbuf(self.myPixbuf)
self.image.show()
gtk.gdk.threads_leave()
scan += 1
except Queue.Empty:
print 'myDisplay finished!'
pass
def quitGUI(obj):
print 'Currently active threads: %s' % threading.enumerate()
gtk.main_quit()
if __name__ == '__main__':
# Create socket (IPv4 protocol, datagram (UDP)) and bind to address
socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
host = '192.168.1.5'
port = 1024
socketUDP.bind((host, port))
# Data parameters
samplesPerScan = 256
packetsPerSecond = 1200
packetSize = 512
duration = 1 # For now, set a fixed duration to log data
numScans = int(packetsPerSecond * duration)
# Create array to store data
data = numpy.zeros((samplesPerScan, numScans), dtype=numpy.uint16)
# Create queue for displaying from
readDataQueue = Queue.Queue(numScans)
# Build GUI from Glade XML file
builder = gtk.Builder()
builder.add_from_file('GroundVue.glade')
window = builder.get_object('mainwindow')
window.connect('destroy', quitGUI)
view = builder.get_object('viewport')
image = gtk.Image()
view.add(image)
viewArea = (1200, samplesPerScan)
# Instantiate & start threads
myServer = readFromUDPSocket(socketUDP, readDataQueue, packetSize, numScans)
myDisplay = displayWithGTK(readDataQueue, image, viewArea)
myServer.start()
myDisplay.start()
gtk.gdk.threads_enter()
gtk.main()
gtk.gdk.threads_leave()
print 'gtk.main finished!'
