A Server and client for proxying local ports through public interfaces


A Node.js client/server implementation of a secure tunnel over TLS/SSL. Useful for exposing local servers on public hosts. Initially implemented to expose a local server to browsers provided by BrowserStack to integrate their beta API with test scripts.

The idea is simple.

  • A server runs on a public host accepting connections on a public host name, let's say ""
  • Initially only one port will be open and accepting connections, eg. 8080
  • On your local machine you start a client that connects to using a TLS socket and let it know what local port it should expose, eg. 8000
  • The server assigns another port for use with that client and starts listening on it using an ordinary net socket, notifying the client on which port it will listen, eg 8081
  • When a third party tries to connect to the server asks the client to make another connection using TLS to handle the traffic going through
  • The client does this and pipes all traffic to and from the third party on and localhost:8000
  • Server or client can be instantiated within a Node.js context
  • Server can be configured to only accept connections from known clients (using SSL certificates), preventing strangers using your resources
  • Client can be configured to validate against a known list of servers (using SSL certificates), preventing anyone from masquerading as your server
  • Server can be configured to expose a predefined set of ports
npm install tls-tunnel


To instantiate and start a server

var Server = require('tls-tunnel').Server;
var server = new Server({
  port: 8080,   // port to listen for client connections 
  key: fs.readFileSync('./keys/server-key.pem'),    // server's private key 
  cert: fs.readFileSync('./keys/server-cert.pem'),  // server's SSL certificate 
  ca: [fs.readFileSync('./keys/client-cert.pem')],  // list of authorized client SSL certificates 
  forwardedPorts: {
    start: 8081,    // Start of port range to assign to connecting clients 
    count: 10       // maximum number of ports and hence clients that can be supported 
  timeout: 5000 // Timeout in milliseconds to use when waiting for a client to provide a tunnel connection 
server.start(function() {
  // server should be listening on port 8080 now 
  server.stop(function() {
    // server should have ended all connections and stopped 

To instantiate and connect a client

var http = require('http');
var Client = require('tls-tunnel').Client;
var client = new Client({
  host: '',  // the host where the server is running 
  port: 8080                // the port on which the server is running 
  key: fs.readFileSync('./keys/client-key.pem'),    // client's private key 
  cert: fs.readFileSync('./keys/client-cert.pem'),  // client's SSL certificate 
  ca: [fs.readFileSync('./keys/server-cert.pem')],  // list of authorized server SSL certificates 
  targetPort: 8000, // the local port to expose through the tunnel 
  timeout: 5000 // Timeout in milliseconds to use when waiting for a server to assign a public port 
client.connect(function(errorport) {
  if (error) {
    // errors could include not having enough ports available on 
    // the server to support another 
  } else {
    // only if no errors were encountered will the <port> parameter 
    // contain the public port that was assigned for the tunnel 
    http.get('' + port, function(res) {
      // should receive a response from localhost:8000 here 
      client.disconnect(function() {
        // client should have ended all connections 

See the test/keys folder for certificates used by the tests. These can be regenerated at anytime using either (OSX, Linux) or keys.bat (Windows). These scripts use OpenSSL. OSX and Linux most likely already ship with OpenSSL. If using Windows you will need to install OpenSSL first.

It should be noted that for the client to authorize server certificates they need to have the correct hosts listed as altnames in the v3 extensions (although this doesn't seem to be required on Windows).

  • Tunnel should be protocol agnostic
    • I thought this would be a given but currently
      • Net connections work
      • HTTP works
      • TLS connections partially work
      • HTTPS does not work
  • Server or client should be runnable from the shell
  • Client should be configurable to only accept a limited number of connections
  • Test keys and certs need to be generated when running tests as they will eventually expire

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using ./ or .\grunt.bat.

(Nothing yet)

Copyright (c) 2012 Peter Halliday
Licensed under the MIT license.