Python : How to close a UDP socket while is waiting for data in recv ?
- by alexroat
Hello,
let's consider this code in python:
import socket
import threading
import sys
import select
class UDPServer:
def __init__(self):
self.s=None
self.t=None
def start(self,port=8888):
if not self.s:
self.s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
self.s.bind(("",port))
self.t=threading.Thread(target=self.run)
self.t.start()
def stop(self):
if self.s:
self.s.close()
self.t.join()
self.t=None
def run(self):
while True:
try:
#receive data
data,addr=self.s.recvfrom(1024)
self.onPacket(addr,data)
except:
break
self.s=None
def onPacket(self,addr,data):
print addr,data
us=UDPServer()
while True:
sys.stdout.write("UDP server> ")
cmd=sys.stdin.readline()
if cmd=="start\n":
print "starting server..."
us.start(8888)
print "done"
elif cmd=="stop\n":
print "stopping server..."
us.stop()
print "done"
elif cmd=="quit\n":
print "Quitting ..."
us.stop()
break;
print "bye bye"
It runs an interactive shell with which I can start and stop an UDP server.
The server is implemented through a class which launches a thread in which there's a infinite loop of recv/*onPacket* callback inside a try/except block which should detect the error and the exits from the loop.
What I expect is that when I type "stop" on the shell the socket is closed and an exception is raised by the recvfrom function because of the invalidation of the file descriptor.
Instead, it seems that recvfrom still to block the thread waiting for data even after the close call.
Why this strange behavior ?
I've always used this patter to implements an UDP server in C++ and JAVA and it always worked.
I've tried also with a "select" passing a list with the socket to the xread argument, in order to get an event of file descriptor disruption from select instead that from recvfrom, but select seems to be "insensible" to the close too.
I need to have a unique code which maintain the same behavior on Linux and Windows with python 2.5 - 2.6.
Thanks.
