1 file screen capturing server depended on phantomjs

capturing_server.js

var page = require('webpage').create();
var server = require('webserver').create();
var system = require('system');
var host, port;

if (system.args.length !== 2) {
    console.log('Usage: server.js <some port>');
    phantom.exit(1);
} else {
    port = system.args[1];
    var service = server.listen(port, function (request, response) {
        console.log(JSON.stringify(request, null, 4));

        if (request.method != 'GET') {
            response.statusCode = 403;
            response.headers = {
                "Cache": "no-cache",
                "Content-Type": "text/html"
            };
            response.write("This service allow GET request only");
            response.close();
            return;
        }

        var validRequestPlease = function (message) {
            response.statusCode = 200;
            response.headers = {
                "Cache": "no-cache",
                "Content-Type": "text/html"
            };
            response.write("Please send valid request: " + message);
            response.close();
        };

        url = request.url;
        if (url == '/') {
            validRequestPlease("Please point the url you want to capture");
            return;
        }
        target_url = decodeURIComponent(url.slice(1, url.length)).replace(":/", "://");
        console.log(target_url);

        page.open(target_url, function (status) {
            console.log(status);
            if (status == "fail") {
                validRequestPlease("some error occurred. " + err);
                return;
            } else {
                page.evaluate(function () {
                    document.body.bgColor = 'white';
                });
                page.render(target_url.replace(/:|\/|\./g, "_") + '.png');
                var b64 = page.renderBase64("PNG");
                response.statusCode = 200;
                response.headers = {
                    "Cache": "no-cache",
                    "Content-Type": "image/png;base64"
                };
                response.write(b64);
                response.close();
            }
        });
    });

    if (service) {
        console.log('Web server running on port ' + port);
    } else {
        console.log('Error: Could not create web server listening on port ' + port);
        phantom.exit();
    }
}