Connecting twice with twisted - how to do that correctly?

Question

I want to use twisted (and StarPy which is a protocol implementation for asterisk ami) to connect to an asterisk server. The application initiates a outgoing fax there. I found

Answer 1

As iny said, you need to do everything with just one call to reactor.run and reactor.stop.

If we consider the example code you posted, we see that it takes these steps:

1. Start the reactor
   • Connect, send a fax, disconnect
   • Stop the reactor
   • Start the reactor
   • Connect, send a fax, disconnect
   • Stop the reactor

If we only delete steps 3 and 4, then the program will actually be doing a pretty reasonable thing.

Here's how you implemented step 3:

def onLogoff( result ):
    print "Logoff erfolgt"
    reactor.stop()

This caused the first call to reactor.run to return, clearing the way for your implementation of step 4:

reactor.callWhenRunning( main )
reactor.run(installSignalHandlers=0)

So, the general idea here is going to be to jump right to step 5 instead of doing step 3 and 4. Consider what might happen if you redefine onLogoff like this:

def onLogoff( result ):
    print "Logoff erfolgt"
    main()

and deleting the last three lines of your example. This will actually give you an infinite loop, since the same onLogoff runs after the 2nd disconnect and starts a 3rd connection. However, you might remedy this with a parameter to the main function to control the restart behavior.

Once this makes sense, you may want to think about moving the retry logout out of the main function and into a callback defined in the __main__ block. This is a big part of the power of Deferreds: it lets you keep proper separation between the implementation of an event source (in this case, your fax sending function) and the code for dealing with the resulting events (sending a second fax, or exiting, in this case).