from twisted.internet import protocol, reactor

class Echo(protocol.Protocol):
    def dataReceived(self, data):
        print("DONE")
        self.transport.write(data)
   def connectionMade(self):
       self.transport.write("Hello, world!")


class EchoFactory(protocol.Factory):
    def buildProtocol(self, addr):
        return Echo()

reactor.listenTCP(8080, EchoFactory())
reactor.run()