Howto connect two programs with Twisted

Question

I have an echoserver in Twisted that needs to get input from an echoclient. The echocient is a GUI (Panda3D). The client just sends a short message when a button is clicked.

So I have messages to send at irregular times (only when button is clicked).

How can I have a permanent connection (the reactor.run() is already started at the beginning of the client program) and send messages.

I don't want to write a polling mechanism in EchoClient/connectionMade. I saw an example of gtk+ but cannot translate it to Panda. How to go about. The code hereunder is not working at all but gives you an idea of what I want (basically permanent connection and once in a while the user sends something when pressing a button).

from direct.showbase.ShowBase import ShowBase
from direct.gui.DirectButton import DirectButton
from panda3d.core import Vec3
from direct.task import Task

from twisted.internet import protocol, reactor, defer
from twisted.internet.task import LoopingCall
from twisted.spread import pb

FRAMERATE = 32

class LoginDialog:
   def __init__(self, deferred):
     self.deferredResult = deferred

class EchoClient(ShowBase, protocol.Protocol):
   def __init__(self):
      ShowBase.__init__(self)

      self.echoer = echoer   
      self.button = DirectButton(pos = Vec3(.1,0,.1), text = "Send request",
               scale = .1, pad = (.5, .5),
               rolloverSound = None, clickSound = None,
               command = self.Request)

   def Request():
      self.echoer.transport.write("Message from client")

   def dataReceived(self, data):
       print "Server said: ", data

cf = pb.PBClientFactory()
cf.getRootObject().addCallback(EchoClient)
reactor.connectTCP("localhost", 17000, cf)
LoopingCall(taskMgr.step).start(1 / FRAMERATE)
reactor.run()

score 1 · Answer 1 · answered Nov 17 '13 at 20:21

1

If you make the client and the server part of the same process then you'll always (well, practically always) be able to pass information from one to the other.

If you make the client and the server different processes then there is probably no solution that satisfies your requirements.

You always have to do something to establish a connection between two processes and there's always a chance it might go away. Sorry.

answered Nov 17 '13 at 20:21

Jean-Paul Calderone

47,755
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The problem is not to get or maintain a connection. It is to get a message across from a running program. In all examples I see a connection is made, and messages are sent upon creation of the connection. Then the connection is terminated. I don't want the reactor.run() to terminate because I don't want to terminate the running application. But how can the application, for example after 1 minute if a user triggers an event, pass a new message to the server? – user2279550 Nov 17 '13 at 21:58
Sorry, that sounds like a completely different question than the one you wrote up. https://twistedmatrix.com/documents/current/core/howto/time.html – Jean-Paul Calderone Nov 18 '13 at 15:55

score 0 · Answer 2 · answered Nov 21 '13 at 23:14

0

have a look at multiprocessing: http://docs.python.org/2/library/multiprocessing.html

you can start and join different processes as well as message between them.

answered Nov 21 '13 at 23:14

samkhan13

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user2279550 · Answer 3 · 2013-11-23T14:26:45.613

I found the answer. Now I have a program that sends a message to a server once a button is pushed. I used a ClientCreator to create an EchoClient. Like this:

      self.clientcreate = protocol.ClientCreator(reactor, EchoClient)
      self.clientcreate.connectTCP(host, port).addCallbacks(self.connectionMade,
               self.connectionFailed)

Now when I connectTCP, and make a connection it calls self.ConnectionMade upon success. Thereby it also gives the EchoClient to the function. So I can store it (self.client = echoclient), and use it when I want (could not achieve this via Factories).

For instance the button calls the function Request and there I can directly use the transport.write command, because I have the client now. So self.client.transport.write('whatever').

If people did not understand what I wanted before, have better ideas to get this done, I would like to see their comments (i want to learn).

The complete code (Client only):

from twisted.internet import protocol, reactor, defer
from twisted.internet.task import LoopingCall

from direct.showbase.ShowBase import ShowBase
from direct.gui.DirectButton import DirectButton
from panda3d.core import Vec3
from direct.task import Task

FRAMERATE = 32

class ButtonDialog(ShowBase):
   def __init__(self):

      ShowBase.__init__(self)

      self.button = DirectButton(pos = Vec3(.1,0,.1), text = "Send request",
               scale = .1, pad = (.5, .5),
               rolloverSound = None, clickSound = None,
               command = self.Request) 

      host = "localhost"
      port = 17001

      self.clientcreate = protocol.ClientCreator(reactor, EchoClient)
      self.clientcreate.connectTCP(host, port).addCallbacks(self.connectionMade,
               self.connectionFailed)

   def connectionFailed(self, f):
       print "Connection Failed:", f
       reactor.stop()

   def connectionMade(self, echoclient):
       self.client = echoclient

   def Request(self):
       self.client.transport.write("Message from button")   

class EchoClient(protocol.Protocol):

   def dataReceived(self, data):
       print "Server said: ", data

   def connectionLost(self, err):
       print "Connection is lost: " + str(err)
       reactor.stop()

ButtonDialog()
LoopingCall(taskMgr.step).start(1 / FRAMERATE)
reactor.run()

Howto connect two programs with Twisted

3 Answers3