The phone has an internal web server that lets the user customise a number of options.  The one I’m interested in is ‘Action URI’.  When a call comes through to my phone, I can enter a URI that my phone will request.  I can send arbitrary parameters in the query string, e.g. a message or the phone number of the caller.  My solution involves a PHP script that the phone can request, a simple Perl socket server sitting listening on my laptop, and a simpel Perl Tk script that will open a window to alert me to the call.

The PHP script that my phone requests is quite simple:

// Hostname of machine
$host = 'somehost';
// Port to connect to
$port = '7890';
$timeout = 30;
$message = $_GET['message'];

$socket = fsockopen($host, $port, $errnum, $errstr, $timeout);
if (!is_resource($socket))
{
exit("Cannot connect: " . $errnum . " " . $errstr);
}
else
{
fputs($socket, $message);
}
fclose($socket);

This script is called from my phone and connects to the socket server listening on my laptop. The code for the corresponding socket server follows:

use strict;
use IO::Socket;
use Net::hostent;

my $PORT = 7890;
my $IP = '192.168.0.1';

my $serverSocket = IO::Socket::INET->new(
    Proto => 'tcp',
    LocalHost => $IP,
    LocalPort => $PORT,
    Listen => SOMAXCONN,
    Reuse => 1,
) or die("Cannot create socket: $!\n");

while (my $clientSocket = $serverSocket->accept())
{
    $clientSocket->autoflush(1);
    while (<$clientSocket>)
    {
        `/path/to/tk/script/showMessage.pl "$_"`;
    }
    close($clientSocket);
}

This Perl script listens in the background for incoming connections and passes any data it receives to a Perl TK script that displays this data in the form of a simple window on display 0:0. Here’s the code for th Perl Tk srcript:

use strict;
use Tk;
use Tk::Font;

my $message = $ARGV[0];

my $mainWindow = MainWindow->new();
$mainWindow->minsize(qw(500 200));
$mainWindow->title("Incoming Call");
$mainWindow->configure(-background => 'white');

my $font = $mainWindow->Font(
    -family => 'Arial',
    -size => '24',
);

my $acceptButton = $mainWindow->Button(
    -text => $message,
    -background => 'red',
    -command => \&exit,
    -foreground => 'white',
    -font => $font,
);

$acceptButton->pack(
    -side => 'bottom',
    -expand => 1,
    -fill => 'both'
);

$mainWindow->withdraw();
$mainWindow->update();
my $winXPos = int(($mainWindow->screenwidth - $mainWindow->width) / 2);
my $winYPos = int(($mainWindow->screenheight - $mainWindow->height) / 2);
$mainWindow->geometry("+$winXPos+$winYPos");
$mainWindow->deiconify();

MainLoop();

There’s no doubt about it, this combination of scripts is crude, insecure, and really more of a proof of concept. Nonetheless, it serves my purposes and hopefully can tidy it up as time allows.