Question

I m trying to build a DNS server in python. It must listen two ports (8007 - client, 8008 - admin). The client only send an URL and receives the respective IP. The admin has permissions to change the DNS table (add, remove,.. doesn t matter to this right now).

So my question is: how do I implement the server listening continuously on the two ports for any eventual request (we can have several clients at the same time but only one admin when he is operating)

my Server with one listening port:

from SocketServer import * from threading import * from string import * import socket

    class Server(ForkingMixIn, TCPServer): pass  #fork for each client

    class Handler(StreamRequestHandler):

        def handle(self):
            addr = self.request.getpeername()
            print  Got connection from , addr
            data=(self.request.recv(1024)).strip()

            if data not in dic: #dic -> dictionary with URL:IP
                self.wfile.write( 0.0.0.0 )
            else:
                self.wfile.write(dic.get(data))


    server = Server((  , 8007), Handler)
    server.serve_forever()

Answer 1

No need to use threads.

Use twisted.

TwistedNames has support out of the box for a dns server. You can customize it as needed or read its source as base when you build yours.

Answer 2

You can use non-blocking sockets, and use the select call to read from the socket. This Sockets Programming HOWTO for Python article has a section on non-blocking sockets in Python that will help.

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