newbie udp socket question

[Andrew Bennetts]

On Sun, May 11, 2003 at 02:13:25AM +0200, p@ wrote:
> Hi list,
> 
> I have made the following UDP client:
> 
> class UdpClientSocket:
>     def __init__(self,address,port,request):
>         sock = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
>         sock.sendto(str(request),address)
>         response = sock.recv(port) #response here
>         command = response[0]
>         if command =='\x02':
>             print 'server is still alive'
>         if command =='\x04':
>             print 'server tcp queue accepted'
>         if command =='\x06':
>             print 'Member address recieved'
>         if command =='\x08':
>             print 'cluster update redirected'
>         
>         sock.close()
> 
> udpc = UdpClientSocket(('localhost',serverPort),clientPort,'\x01')
> 
> 
> The problem is if I don't get any response from the server it will block
> forever. So how do I implement a timeout for this?
> I have found a tcp-timeout-socket but none for udp...

Personally, I'd just use Twisted :)

Here's an untested example of your code implemented in Twisted, complete
with a 10 second timeout.


from twisted.internet.protocol import ConnectedDatagramProtocol
from twisted.internet import reactor

class MyUDPClient(ConnectedDatagramProtocol):
    def __init__(self, request):
        self.request = str(request)

    def startProtocol(self):
        self.transport.write(self.request)
    
    def datagramReceived(self, data):
        if command =='\x02':
            print 'server is still alive'
        if command =='\x04':
            print 'server tcp queue accepted'
        if command =='\x06':
            print 'Member address received'
        if command =='\x08':
            print 'cluster update redirected'
        self.transport.loseConnection()
        reactor.stop()

reactor.connectUDP('localhost', serverPort, MyUDPClient('\x01'),
                   localport=clientPort)
reactor.callLater(10, reactor.stop)    # 10 second timeout
reactor.run()


You could use non-blocking sockets and a select loop to achieve this
manually, but I find letting a library do all hard work for me much easier
:)

-Andrew.