posa pa 3

gistfile1.txt

"""
POSA PA 3 program
Echo Server

built and tested using python 2.7.2 and Twisted 12.0.0
"""

import sys



from twisted.internet.protocol import Protocol, Factory
from twisted.internet import reactor
from twisted.python import log

class EchoServerHandler(Protocol):
    """Event Handler - Reactor passes control to it after receiving data event"""
    def connectionMade(self):
        log.msg("Client connection")
        self.transport.write("Hi there. I'm an Echo Server. You can stop me by sending quit message\n")

    def dataReceived(self, data):
        """
        Similar to Wrapper Facade - called by Reactor after receiving data from socket stream
        """
        log.msg("data received %s bytes: %s" % (len(data),data))
        self.transport.write(data)
        if "quit" in data:
            self.transport.write("Bye bye\n")
            self.transport.loseConnection()
            reactor.callFromThread(reactor.stop)


    def connectionLost(self, reason):
        log.msg("client disconnected")


class EchoServerFactory(Factory):
    """Acceptor - handles connection event - takes care about instantiating Event Handler object"""
    def buildProtocol(self, addr):
        log.msg("EchoServerFactory %s" % addr)
        return EchoServerHandler()



def main():
    """
     Main program
     Starts Echo Server to listen on 5555 port
     You can test it with command:
     telnet localhost 5555
    """
    log.startLogging(sys.stdout)
    """twisted.internet.reactor module takes care about running server - configures TCP listener and runs the event loop
    thus it implements Reactor pattern - handles service requests that are delivered concurrently to an application by one or more clients

    Also the reactor provides basic interfaces to a number of services, including network communications, threading, and event dispatching - thus it implements Wrapper Facade pattern
    """
    reactor.listenTCP(5555, EchoServerFactory())
    reactor.run()

if __name__=='__main__':
    main()