Fetch value from website and control relay?

I got a quite unusual question today from a client. They provide a mission-critical service where it's important that people are notified when a certain event happens. Currently they have an API that simply writes out TRUE or FALSE, when accessed by a web browser, depending on the state of their alert.

They want to take this even further, so they want to have a PC which would fetch the value from their existing API on a continuous basis, and depending on the value, toggle a relay, which would turn on/off an alarm 开发者_如何学编程or warning light in their office.

I have no idea of how one could build such a thing, as I work only on web applications. It doesn't sound like a project requiring too many braincells, but certainly a challenge for me. What languages do I need to learn to accomplish something like this?

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Since the software event will trigger a physical action (turning on a light) it will require you to interface with some sort of electronic device.

A good start would be Arduino. It's open-source hardware and let's you interface with the board using a variant of C++.

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This project consists of two parts:

1. Connect the internet to the PC. For example using Perl.

   use LWP::Simple 'get';
   
   
   my $url   = 'http://...';
   my $value = get($url);
   if ($value =~ m/TRUE/) {
       switch_relay(1);
   }
   elsif ($value =~ m/FALSE/) {
       switch_relay(0);
   }
   

2. Connect the PC to some hardware, switch_relay in the example. There are a few ways to do this.

   • You could use X10. But I haven't used it, so I can be more helpful with that.
   • There is the Velleman K8055, a USB interface board, which can be connected with USB. I used this with Perl and it worked really well.
   • Or some other USB to hardware device, like Arduino, would work as well.
   • Even simpler: If you use an USB lamp, you can just power off the USB power of that device.

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X10 + curl + any language that lets you communicate over a serial port:

http://www.smarthome.com/1140/X10-Activehome-CM11A-Computer-Interface-CM11A/p.aspx

http://www.smarthome.com/manuals/protocol.txt

http://curl.haxx.se/

Perhaps even just a batch file to tie it all together, including http://www.computerhope.com/cttyhlp.htm + 'echo' for serial communication