Programming Jabber

Sensor poll/presence push loop

Now that we’ve set everything up, determined the initial coffee status, and connected to the Jabber server, we’re ready to start the main loop:

# Main loop: check Jabber and RCX
while (1) {
  defined($jabber->Process(GRAIN)) or
    die "The connection to the Jabber server was broken\n";
  my $s = &set_status($rcx->Poll(9, SENSOR));
  &set_presence($jabber, $s) if defined $s;
}

The while (1) loop is a bit of a giveaway. This script won’t stop until you force it to by entering Ctrl-C—but that’s essentially what we want. In the loop, we call the Process() method on the Jabber connection object in $jabber.

Process() is the equivalent of the Jabberpy’s process() method in the Python scripts. Process() waits around for up to the number of seconds specified as the single argument (or not at all if no argument is specified) for XML to appear on the stream connection from the Jabber server. If complete fragments do appear, callbacks, defined in the connection object, are called with the elements (<iq/>, <message/>, and <presence/>) that the fragments represent. This is in the same way as, for example, callbacks are used in the Python scripts using the Jabberpy library. The setup_Jabber(), which will be discussed in the next section, is where the callback definition is made.

Net::Jabber’s Process() method returns undef if the connection to the Jabber server is terminated while waiting for XML. The undef value is dealt with appropriately by ending the script.

The ...