server.js

var fs      = require('fs');
var http    = require('http');
var express = require('express');

var app = express();

app.use(express.static(__dirname + '/../srv'));

fs.writeFile('/sys/class/gpio/export', '34', function(err) {
    if (err) throw err;

    app.get('/light', function(req, res, next) {
        fs.readFile('/sys/class/gpio/gpio34/value', function(err, result) {
            if (err) return next(err);
            
            res.status(200);
            res.format({
                json: function() {
                    res.json({ on: Boolean(result.toString()) });
                }
            });
        });
    });
    app.put('/light', function(req, res) {
        var state = (res.body.on) ? '1' : '0';
        
        fs.writeFile('/sys/class/gpio/gpio34/value', state, function(err) {
            if (err) return next(err);
            
            res.status(200);
            res.format({
                json: function() {
                    res.json();
                }
            });
        });
    });
});

app.use(express.errorHandler());

http.createServer(app).listen(8080);