the client can send a request get a reply

from twisted.internet import reactor, protocol, defer
from twisted.protocols import basic

class Client(basic.LineReceiver):
    
    # Internal
    def lineReceived(self, data):
        self.d.callback(data)
        
    def command(self, cmd):
        self.sendLine(cmd)
        self.d = defer.Deferred()
        return self.d

    # public API
    def random(self): 
        def gotRandom(number):
            return int(number)
        return self.command("random?").addCallback(gotRandom)

    def classified(self): 
        return self.command("classified?")

    # User code, this is actually the main()
    @defer.inlineCallbacks
    def connectionMade(self):
        print (yield self.random(None))
        print (yield self.classified(None))
        reactor.stop()


factory = protocol.ClientFactory()
factory.protocol = Client
reactor.connectTCP("localhost", 6789, factory)
reactor.run()