Python asyncore UDP server

Question

I am writing server application in Python that listens for requests, processes them, and sends a response.

All req/resp are send from the same address and port to the server application. I need to recv/send messages simultaneously, and the server need to recieve/send messages from/to the same port and address. I found some tutorials for asynchore sockets, but there are only examples for TCP connections.

Unfortunately, I need UDP. When I change SOCK_STREAM to SOCK_DGRAM in the create method, I get an error.

return getattr(self._sock,name)(*args)
socket.error: [Errno 95] Operation not supported

I tried to use twisted, but I dont know how to write the sender part, which can bind to the same port as its listening. The last result was blocked port.

Is there any way how to use asyncore sockets with UDP or how to use twisted to send from the same port? Some examples will be higly appreciated.

Cleome

The question is badly formed. Should read How to create a Python UDP server or simply Python UDP server. The selected answer does not in fact relate at all to the question in the title while providing a solution to your problem. – Allonge

Answer 1

You can pretty much just write the sending and receiving part of your code and they'll work together. Note that you can send and receive on a single listening UDP socket - you don't need one for each (particularly if you want to send from and receive on the same address).

from __future__ import print_function

from sys import stdout

from twisted.python.log import startLogging
from twisted.internet import reactor
from twisted.internet.protocol import DatagramProtocol

class SomeUDP(DatagramProtocol):
    def datagramReceived(self, datagram, address):
        print(u"Got a datagram of {} bytes.".format(len(datagram)))

    def sendFoo(self, foo, ip, port):
        self.transport.write(
            (u"Foo datagram: {}".format(foo)).encode("utf-8"),
            (ip, port))

class SomeSender(object):
    def __init__(self, proto):
        self.proto = proto

    def start(self):
        reactor.callLater(3, self._send)

    def _send(self):
        self.proto.sendFoo(u"Hello or whatever", b"127.0.0.1", 12345)
        self.start()

startLogging(stdout)

proto = SomeUDP()
reactor.listenUDP(12345, proto)

SomeSender(proto).start()

reactor.run()

Boggart

I am probably mistaken , but the SomeSender isnt sending the message on the same port 12345 ? Because what i need , is this : Client send request with src port 1111 -> to server with dst port 2222 . Server processed it, sends response with src port 2222 to client -> dst port 1111 . (at the same time , when the server sends response , another request are received on the port 2222) – Cleome

It is sending the messages from the same port. Only one port bound and used by this example. – Boggart