Modified WWW blink version of the one created by David here: http://www.appsaloon.be/blog/node-js-arduino-yun/

www-blink.js

console.log('WWW blink start ...');
                               
var ledPin = 13;
var firmata = require('firmata');
                                 
var board = new firmata.Board("/dev/ttyATH0", function(err) {
                                                             
  if (err) {
    console.log(err);
    board.reset();   
    return;       
  } else { 
    console.log('connected...');
                             
    console.log('board.firmware: ', board.firmware);   
                                                       
    board.pinMode(ledPin, board.MODES.OUTPUT);
                                              
    var url = require('url');
    var http = require('http');
                               
    http.createServer(function(request, response) {
      var params = url.parse(request.url, true).query;
                                                      
      if (params.value.toLowerCase() == 'high') {     
        board.digitalWrite(ledPin, board.HIGH);       
      } else {                                   
        board.digitalWrite(ledPin, board.LOW);   
      }                                          
                                                               
      response.writeHead(200);                                 
      response.write("The value written was: " + params.value);
      response.end();                                          
                                                               
    }.bind(this)).listen(8080);                                
                                              
    console.log('Listening on port 8080 ...');
  }                                           
});