node-proxy.js

'use strict';

var http = require('http');
var net = require('net');

/*
 * Usage : node node-proxy.js [-d] [-p 5555]
 */

var debugging = 0;

function parseHostPort(hostString, defaultPort) {
    var host = hostString;
    var port = defaultPort;

    var result = /^([^:]+)(?::([0-9]+))?$/.exec(hostString);
    if (result != null) {
        host = result[1];
        port = result[2] || port;
    }

    return {host: host, port: port};
}

// handle a HTTP proxy request
function httpUserRequest(userRequest, userResponse) {
    if (debugging) console.log('  > request: %s', userRequest.url);

    var httpVersion = userRequest.httpVersion;
    var hostport = parseHostPort(userRequest.headers.host, 80);

    // have to extract the path from the requested URL
    var path = userRequest.url;
    var result = /^[a-zA-Z]+:\/\/[^\/]+(\/.*)?$/.exec(userRequest.url);
    if (result != null) {
        path = (result[1].length > 0) ? result[1] : "/";
    }

    var options = {
        'host': hostport.host,
        'port': hostport.port,
        'method': userRequest.method,
        'path': path,
        'agent': userRequest.agent,
        'auth': userRequest.auth,
        'headers': userRequest.headers
    };

    if (debugging) console.log('  > options: ' + JSON.stringify(options, null, 2));

    var proxyRequest = http.request(options,
        function (proxyResponse) {
            if (debugging) console.log('  > request headers: ' + JSON.stringify(options['headers'], null, 2));
            if (debugging) console.log('  < response ' + proxyResponse.statusCode + ' headers: ' + JSON.stringify(proxyResponse.headers, null, 2));

            userResponse.writeHead(
                proxyResponse.statusCode,
                proxyResponse.headers
            );

            proxyResponse.pipe(userResponse);
        }
    );

    proxyRequest.on('error',
        function (error) {
            userResponse.writeHead(500);
            userResponse.write(error);
            userResponse.end();
        }
    );

    userRequest.pipe(proxyRequest);
}

function main() {
    var port = 5555; // default port if none on command line

    // check for any command line arguments
    for (var argn = 2; argn < process.argv.length; argn++) {
        if (process.argv[argn] === '-p') {
            port = parseInt(process.argv[argn + 1]);
            argn++;
            continue;
        }
        if (process.argv[argn] === '-d') {
            debugging = 1;
            continue;
        }
    }

    if (debugging) console.log('server listening on port ' + port);

    // start HTTP server with custom request handler callback function
    var server = http.createServer(httpUserRequest).listen(port);

    // add handler for HTTPS (which issues a CONNECT to the proxy)
    server.on('connect',
        function (request, socketRequest, headers) {
            var url = request['url'];
            var httpVersion = request['httpVersion'];

            var hostport = parseHostPort(url, 443);

            if (debugging) console.log('  = will connect to ' + hostport.host + ':' + hostport.port);

            // set up TCP connection
            var proxySocket = new net.Socket();

            proxySocket.connect(
                parseInt(hostport.port), hostport.host,
                function () {
                    if (debugging) console.log('  < connected to ' + hostport.host + ':' + hostport.port);
                    if (debugging) console.log('  > writing head of length ' + headers.length);

                    proxySocket.write(headers);
                    socketRequest.write("HTTP/" + httpVersion + " 200 Connection established\r\n\r\n");
                }
            );

            proxySocket.pipe(socketRequest);
            socketRequest.pipe(proxySocket);

            proxySocket.on('error',
                function (err) {
                    socketRequest.write("HTTP/" + httpVersion + " 500 Connection error\r\n\r\n");
                    if (debugging) console.log('  < ERR: ' + err);
                    socketRequest.end();
                }
            );

            socketRequest.on('error',
                function (err) {
                    if (debugging) console.log('  > ERR: ' + err);
                    proxySocket.end();
                }
            );
        }
    ); // HTTPS connect listener
}

main();