On Thu, 16 Oct 2008 10:47:59 -0700 (PDT), Nima Ghanavatian <nimag@rogers.com> wrote:

Hi,

I have a server which can handle multiple connections. At any given time, I want to send out a ping to see who is still listening to this server.

For this I scan through my list of ip's and send out a msg with

factory = ClientFactory() factory.protocol = caller factory.message = self.message factory.alive = 0 reactor.connectTCP(self.ip, self.port, factory)

and wait on the response. This is done from within an application daemon, so no reactor.run() is required.

I'm not sure I understand. You have a server, but you're making outgoing connects from it to other servers. This will tell you what other servers are still listening. Is that what "to see who is still listening to this server" means?

How can I send a message out and wait for the response before proceeding? I tried using deferreds a bunch of different ways but I can't seem to get it going. Oh and I should clarify I want the response to be in the original stream, not in the thread created by connectTCP/dataReceived/etc...

There are only two or three APIs in Twisted which will run your code in a thread other than the reactor thread. None of the connection setup APIs or the network event APIs do this. However, I'm confused by your comparison of "the original stream" to "the thread created ...". These aren't really comparable things. When you set up a TCP connection with reactor.connectTCP, data received via the resulting connection is passed to the dataReceived method of the protocol instance returned by the factory's buildProtocol method. If you want the data, that's how you get it: implement dataReceived to handle it in the manner you wish. For example, you could create a Deferred which fires with all the data received over a single connection after that connection closes: from twisted.internet.protocol import Protocol, ClientFactory from twisted.internet.defer import Deferred from twisted.python.log import err class GatherOutput(Protocol): def connectionMade(self): self.output = [] def dataReceived(self, data): self.output.append(data) def connectionLost(self, reason): self.factory.dataDeferred.callback(self.output) f = ClientFactory() f.dataDeferred = Deferred() f.protocol = GatherOutput reactor.connectTCP(host, port, f) def gotData(data): print 'Got data', data f.dataDeferred.addCallback(gotData) f.dataDeferred.addErrback(err) reactor.run() Deferreds are the most common way for dealing with potentially long-running (or long-waiting) operations in Twisted. Jean-Paul