diff --git a/.babelrc b/.babelrc
new file mode 100644
index 0000000..ffd53e0
--- /dev/null
+++ b/.babelrc
@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "transform-es2015-modules-commonjs",
+    "transform-async-to-generator",
+  ]
+}
diff --git a/.npmrc b/.npmrc
new file mode 100644
index 0000000..1dab4ed
--- /dev/null
+++ b/.npmrc
@@ -0,0 +1 @@
+save-exact = true
diff --git a/Dockerfile b/Dockerfile
index 8436615..619cd69 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,13 +1,11 @@
-FROM mhart/alpine-node:4.2.1
+FROM mhart/alpine-node:6.3.0
 
 RUN mkdir -p /app
 WORKDIR /app
 
 ADD package.json /app/
 
-RUN apk add --update make git g++ python && \
-    npm install --production && \
-    apk del git make g++ python && \
+RUN npm install --production && \
     rm -rf /tmp/* /root/.npm /root/.node-gyp
 
 ADD . /app
diff --git a/bin/server b/bin/server
index f33fd99..b929958 100755
--- a/bin/server
+++ b/bin/server
@@ -1,12 +1,13 @@
 #!/usr/bin/env node
 
-require('stackup');
-var log = require('bookrc');
-var localenv = require('localenv');
-var debug = require('debug')('localtunnel');
-var optimist = require('optimist');
+require('localenv');
+require('babel-register');
 
-var argv = optimist
+const log = require('bookrc');
+const debug = require('debug')('localtunnel');
+const optimist = require('optimist');
+
+const argv = optimist
     .usage('Usage: $0 --port [num]')
     .options('secure', {
         default: false,
@@ -27,14 +28,18 @@ if (argv.help) {
     process.exit();
 }
 
-var server = require('../server')({
+const server = require('../server')({
     max_tcp_sockets: argv['max-sockets'],
     secure: argv.secure
 });
 
-server.listen(argv.port, function() {
+server.listen(argv.port, () => {
     debug('server listening on port: %d', server.address().port);
 });
 
+process.on('SIGINT', () => {
+    process.exit();
+});
+
 // vim: ft=javascript
 
diff --git a/lib/BindingAgent.js b/lib/BindingAgent.js
index 8aa9ac2..c0d7ad9 100644
--- a/lib/BindingAgent.js
+++ b/lib/BindingAgent.js
@@ -1,6 +1,6 @@
-var http = require('http');
-var util = require('util');
-var assert = require('assert');
+import http from 'http';
+import util from 'util';
+import assert from 'assert';
 
 // binding agent will return a given options.socket as the socket for the agent
 // this is useful if you already have a socket established and want the request
@@ -20,4 +20,4 @@ function create_connection(port, host, options) {
     return this.socket;
 }
 
-module.exports = BindingAgent;
+export default BindingAgent;
diff --git a/lib/rand_id.js b/lib/rand_id.js
index d0b1c13..f76f6d8 100644
--- a/lib/rand_id.js
+++ b/lib/rand_id.js
@@ -1,11 +1,11 @@
 // all url safe
 // can't use uppercase because hostnames are lowercased
-var chars = 'abcdefghijklmnopqrstuvwxyz';
+const chars = 'abcdefghijklmnopqrstuvwxyz';
 
-module.exports = function rand_id() {
-    var randomstring = '';
+export default function rand_id() {
+    let randomstring = '';
     for (var i=0; i<10; ++i) {
-        var rnum = Math.floor(Math.random() * chars.length);
+        const rnum = Math.floor(Math.random() * chars.length);
         randomstring += chars[rnum];
     }
 
diff --git a/package.json b/package.json
index c3cc4a8..907e465 100644
--- a/package.json
+++ b/package.json
@@ -6,24 +6,28 @@
   "license": "MIT",
   "repository": {
     "type": "git",
-    "url": "git://github.com/shtylman/localtunnel-server.git"
+    "url": "git://github.com/localtunnel/server.git"
   },
   "dependencies": {
+    "babel-plugin-transform-async-to-generator": "6.8.0",
+    "babel-plugin-transform-es2015-modules-commonjs": "6.10.3",
+    "babel-polyfill": "6.9.1",
+    "babel-register": "6.9.0",
+    "bluebird": "3.4.1",
     "book": "1.3.1",
     "book-git": "0.0.2",
-    "book-raven": "1.1.0",
+    "book-raven": "1.2.0",
     "bookrc": "0.0.1",
     "debug": "2.2.0",
-    "express": "4.13.3",
-    "http-proxy": "1.12.0",
+    "express": "4.14.0",
+    "http-proxy": "1.14.0",
     "localenv": "0.2.2",
     "on-finished": "2.3.0",
     "optimist": "0.6.1",
-    "stackup": "1.0.1",
-    "tldjs": "1.6.1"
+    "tldjs": "1.6.2"
   },
   "devDependencies": {
-    "mocha": "2.0.1",
+    "mocha": "2.5.3",
     "localtunnel": "1.8.0",
     "ws": "0.8.0"
   },
diff --git a/proxy.js b/proxy.js
index 3d9db14..1000930 100644
--- a/proxy.js
+++ b/proxy.js
@@ -1,28 +1,51 @@
-var net = require('net');
-var EventEmitter = require('events').EventEmitter;
+import net from 'net';
+import EventEmitter from 'events';
+import log from 'bookrc';
+import Debug from 'debug';
 
-var log = require('bookrc');
-var debug = require('debug')('localtunnel-server');
+const debug = Debug('localtunnel:server');
 
-var Proxy = function(opt, cb) {
+const Proxy = function(opt) {
     if (!(this instanceof Proxy)) {
-        return new Proxy(opt, cb);
+        return new Proxy(opt);
     }
 
-    var self = this;
+    const self = this;
 
     self.sockets = [];
     self.waiting = [];
-
-    var id = opt.id;
+    self.id = opt.id;
 
     // default max is 10
-    var max_tcp_sockets = opt.max_tcp_sockets || 10;
+    self.max_tcp_sockets = opt.max_tcp_sockets || 10;
 
     // new tcp server to service requests for this client
-    var client_server = net.createServer();
+    self.server = net.createServer();
 
-    client_server.on('error', function(err) {
+    // track initial user connection setup
+    self.conn_timeout = undefined;
+
+    self.debug = Debug(`localtunnel:server:${self.id}`);
+};
+
+Proxy.prototype.__proto__ = EventEmitter.prototype;
+
+Proxy.prototype.start = function(cb) {
+    const self = this;
+    const server = self.server;
+
+    if (self.started) {
+        cb(new Error('already started'));
+        return;
+    }
+    self.started = true;
+
+    server.on('close', self._cleanup.bind(self));
+    server.on('connection', self._handle_socket.bind(self));
+
+    server.on('error', function(err) {
+        // where do these errors come from?
+        // other side creates a connection and then is killed?
         if (err.code == 'ECONNRESET' || err.code == 'ETIMEDOUT') {
             return;
         }
@@ -30,129 +53,121 @@ var Proxy = function(opt, cb) {
         log.error(err);
     });
 
-    // track initial user connection setup
-    var conn_timeout;
-
-    // user has 5 seconds to connect before their slot is given up
-    function maybe_tcp_close() {
-        clearTimeout(conn_timeout);
-        conn_timeout = setTimeout(function() {
-
-            // sometimes the server is already closed but the event has not fired?
-            try {
-                clearTimeout(conn_timeout);
-                client_server.close();
-            } catch (err) {
-                cleanup();
-            }
-        }, 5000);
-    }
-
-    maybe_tcp_close();
-
-    function cleanup() {
-        debug('closed tcp socket for client(%s)', id);
-
-        clearTimeout(conn_timeout);
-
-        // clear waiting by ending responses, (requests?)
-        self.waiting.forEach(function(waiting) {
-            waiting(null);
-        });
-
-        self.emit('end');
-    }
-
-    // no longer accepting connections for this id
-    client_server.on('close', cleanup);
-
-    // new tcp connection from lt client
-    client_server.on('connection', function(socket) {
-        // no more socket connections allowed
-        if (self.sockets.length >= max_tcp_sockets) {
-            return socket.end();
-        }
-
-        debug('new connection on port: %s', id);
-
-        // a single connection is enough to keep client id slot open
-        clearTimeout(conn_timeout);
-
-        socket.once('close', function(had_error) {
-            debug('client %s closed socket (error: %s)', id, had_error);
-
-            // what if socket was servicing a request at this time?
-            // then it will be put back in available after right?
-
-            // remove this socket
-            var idx = self.sockets.indexOf(socket);
-            if (idx >= 0) {
-                self.sockets.splice(idx, 1);
-            }
-
-            // need to track total sockets, not just active available
-            debug('remaining client sockets: %s', self.sockets.length);
-
-            // no more sockets for this ident
-            if (self.sockets.length === 0) {
-                debug('all client(%s) sockets disconnected', id);
-                maybe_tcp_close();
-            }
-        });
-
-        // close will be emitted after this
-        socket.on('error', function(err) {
-            // we don't log here to avoid logging crap for misbehaving clients
-            socket.destroy();
-        });
-
-        self.sockets.push(socket);
-
-        var wait_cb = self.waiting.shift();
-        if (wait_cb) {
-            debug('handling queued request');
-            self.next_socket(wait_cb);
-        }
-    });
-
-    client_server.listen(function() {
-        var port = client_server.address().port;
-        debug('tcp server listening on port: %d', port);
+    server.listen(function() {
+        const port = server.address().port;
+        self.debug('tcp server listening on port: %d', port);
 
         cb(null, {
             // port for lt client tcp connections
             port: port,
             // maximum number of tcp connections allowed by lt client
-            max_conn_count: max_tcp_sockets
+            max_conn_count: self.max_tcp_sockets
         });
     });
+
+    self._maybe_destroy();
 };
 
-Proxy.prototype.__proto__ = EventEmitter.prototype;
+Proxy.prototype._maybe_destroy = function() {
+    const self = this;
 
-Proxy.prototype.next_socket = function(cb) {
-    var self = this;
+    clearTimeout(self.conn_timeout);
+    self.conn_timeout = setTimeout(function() {
+        // sometimes the server is already closed but the event has not fired?
+        try {
+            clearTimeout(self.conn_timeout);
+            self.server.close();
+        }
+        catch (err) {
+            self._cleanup();
+        }
+    }, 5000);
+}
 
-    // socket is a tcp connection back to the user hosting the site
-    var sock = self.sockets.shift();
+// new socket connection from client for tunneling requests to client
+Proxy.prototype._handle_socket = function(socket) {
+    const self = this;
 
-    // TODO how to handle queue?
-    // queue request
-    if (!sock) {
-        debug('no more client, queue callback');
-        return self.waiting.push(cb);
+    // no more socket connections allowed
+    if (self.sockets.length >= self.max_tcp_sockets) {
+        return socket.end();
     }
 
-    var done_called = false;
-    // put the socket back
-    function done() {
-        if (done_called) {
-            throw new Error('done called multiple times');
+    self.debug('new connection from: %s:%s', socket.address().address, socket.address().port);
+
+    // a single connection is enough to keep client id slot open
+    clearTimeout(self.conn_timeout);
+
+    socket.once('close', function(had_error) {
+        self.debug('closed socket (error: %s)', had_error);
+
+        // what if socket was servicing a request at this time?
+        // then it will be put back in available after right?
+        // we need a list of sockets servicing requests?
+
+        // remove this socket
+        const idx = self.sockets.indexOf(socket);
+        if (idx >= 0) {
+            self.sockets.splice(idx, 1);
         }
 
-        done_called = true;
+        // need to track total sockets, not just active available
+        self.debug('remaining client sockets: %s', self.sockets.length);
+
+        // no more sockets for this ident
+        if (self.sockets.length === 0) {
+            self.debug('all sockets disconnected');
+            self._maybe_destroy();
+        }
+    });
+
+    // close will be emitted after this
+    socket.on('error', function(err) {
+        // we don't log here to avoid logging crap for misbehaving clients
+        socket.destroy();
+    });
+
+    self.sockets.push(socket);
+
+    const wait_cb = self.waiting.shift();
+    if (wait_cb) {
+        self.debug('handling queued request');
+        self.next_socket(wait_cb);
+    }
+};
+
+Proxy.prototype._cleanup = function() {
+    const self = this;
+    self.debug('closed tcp socket for client(%s)', self.id);
+
+    clearTimeout(self.conn_timeout);
+
+    // clear waiting by ending responses, (requests?)
+    self.waiting.forEach(handler => handler(null));
+
+    self.emit('end');
+};
+
+Proxy.prototype.next_socket = function(handler) {
+    const self = this;
+
+    // socket is a tcp connection back to the user hosting the site
+    const sock = self.sockets.shift();
+
+    if (!sock) {
+        self.debug('no more client, queue callback');
+        self.waiting.push(handler);
+        return;
+    }
+
+    self.debug('processing request');
+    handler(sock)
+    .catch((err) => {
+        log.error(err);
+    })
+    .finally(() => {
         if (!sock.destroyed) {
-            debug('retuning socket');
+            self.debug('retuning socket');
             self.sockets.push(sock);
         }
 
@@ -161,19 +176,17 @@ Proxy.prototype.next_socket = function(cb) {
             return;
         }
 
-        var wait = self.waiting.shift();
-        debug('processing queued cb');
+        const wait = self.waiting.shift();
+        self.debug('processing queued cb');
         if (wait) {
-            return self.next_socket(cb);
+            self.next_socket(cb);
+            return;
         }
-    };
-
-    debug('processing request');
-    cb(sock, done);
+    });
 };
 
 Proxy.prototype._done = function() {
-    var self = this;
+    const self = this;
 };
 
-module.exports = Proxy;
+export default Proxy;
diff --git a/server.js b/server.js
index 707c510..87516fa 100644
--- a/server.js
+++ b/server.js
@@ -1,14 +1,19 @@
-var log = require('bookrc');
-var express = require('express');
-var tldjs = require('tldjs');
-var on_finished = require('on-finished');
-var debug = require('debug')('localtunnel-server');
-var http_proxy = require('http-proxy');
-var http = require('http');
+import log from 'bookrc';
+import express from 'express';
+import tldjs from 'tldjs';
+import on_finished from 'on-finished';
+import Debug from 'debug';
+import http_proxy from 'http-proxy';
+import http from 'http';
+import Promise from 'bluebird';
 
-var BindingAgent = require('./lib/BindingAgent');
+import Proxy from './proxy';
+import rand_id from './lib/rand_id';
+import BindingAgent from './lib/BindingAgent';
 
-var proxy = http_proxy.createProxyServer({
+const debug = Debug('localtunnel:server');
+
+const proxy = http_proxy.createProxyServer({
     target: 'http://localtunnel.github.io'
 });
 
@@ -23,51 +28,54 @@ proxy.on('proxyReq', function(proxyReq, req, res, options) {
     proxyReq.setHeader('host', 'localtunnel.github.io');
 });
 
-var Proxy = require('./proxy');
-var rand_id = require('./lib/rand_id');
-
-var PRODUCTION = process.env.NODE_ENV === 'production';
+const PRODUCTION = process.env.NODE_ENV === 'production';
 
 // id -> client http server
-var clients = Object.create(null);
+const clients = Object.create(null);
 
 // proxy statistics
-var stats = {
+const stats = {
     tunnels: 0
 };
 
+// handle proxying a request to a client
+// will wait for a tunnel socket to become available
 function maybe_bounce(req, res, sock, head) {
     // without a hostname, we won't know who the request is for
-    var hostname = req.headers.host;
+    const hostname = req.headers.host;
     if (!hostname) {
         return false;
     }
 
-    var subdomain = tldjs.getSubdomain(hostname);
+    const subdomain = tldjs.getSubdomain(hostname);
     if (!subdomain) {
         return false;
     }
 
-    var client_id = subdomain;
-    var client = clients[client_id];
+    const client = clients[subdomain];
 
     // no such subdomain
     // we use 502 error to the client to signify we can't service the request
     if (!client) {
-        res.statusCode = 502;
-        res.end('localtunnel error: no active client for \'' + client_id + '\'');
-        req.connection.destroy();
+        if (res) {
+            res.statusCode = 502;
+            res.end(`no active client for '${subdomain}'`);
+            req.connection.destroy();
+        }
+        else if (sock) {
+            sock.destroy();
+        }
+
         return true;
     }
 
-    var finished = false;
+    let finished = false;
     if (sock) {
         sock.once('end', function() {
             finished = true;
         });
     }
-
-    if (res) {
+    else if (res) {
         // flag if we already finished before we get a socket
         // we can't respond to these requests
         on_finished(res, function(err) {
@@ -75,16 +83,19 @@ function maybe_bounce(req, res, sock, head) {
             req.connection.destroy();
         });
     }
+    // not something we are expecting, need a sock or a res
+    else {
+        req.connection.destroy();
+        return true;
+    }
 
     // TODO add a timeout, if we run out of sockets, then just 502
 
     // get client port
-    client.next_socket(function(socket, done) {
-        done = done || function() {};
-
+    client.next_socket(async (socket) => {
         // the request already finished or client disconnected
         if (finished) {
-            return done();
+            return;
         }
 
         // happens when client upstream is disconnected
@@ -103,9 +114,9 @@ function maybe_bounce(req, res, sock, head) {
         // and directly pipe the socket data
         // avoids having to rebuild the request and handle upgrades via the http client
         if (res === null) {
-            var arr = [req.method + ' ' + req.url + ' HTTP/' + req.httpVersion];
-            for (var i=0 ; i < (req.rawHeaders.length-1) ; i+=2) {
-                arr.push(req.rawHeaders[i] + ': ' + req.rawHeaders[i+1]);
+            const arr = [`${req.method} ${req.url} HTTP/${req.httpVersion}`];
+            for (let i=0 ; i < (req.rawHeaders.length-1) ; i+=2) {
+                arr.push(`${req.rawHeaders[i]}: ${req.rawHeaders[i+1]}`);
             }
 
             arr.push('');
@@ -113,40 +124,55 @@ function maybe_bounce(req, res, sock, head) {
 
             socket.pipe(sock).pipe(socket);
             socket.write(arr.join('\r\n'));
-            socket.once('end', function() {
-                done();
+
+            await new Promise((resolve) => {
+                socket.once('end', resolve);
             });
 
             return;
         }
 
-        var agent = new BindingAgent({
+        // regular http request
+
+        const agent = new BindingAgent({
             socket: socket
         });
 
-        var opt = {
+        const opt = {
             path: req.url,
             agent: agent,
             method: req.method,
             headers: req.headers
         };
 
-        var client_req = http.request(opt, function(client_res) {
-            // write response code and headers
-            res.writeHead(client_res.statusCode, client_res.headers);
-            
-            client_res.pipe(res);
-            on_finished(client_res, function(err) {
-                done();
-            });
-        });
+        await new Promise((resolve) => {
+            // what if error making this request?
+            const client_req = http.request(opt, function(client_res) {
+                // write response code and headers
+                res.writeHead(client_res.statusCode, client_res.headers);
 
-        req.pipe(client_req);
+                client_res.pipe(res);
+                on_finished(client_res, function(err) {
+                    resolve();
+                });
+            });
+
+            // happens if the other end dies while we are making the request
+            // so we just end the req and move on
+            // we can't really do more with the response here because headers
+            // may already be sent
+            client_req.on('error', (err) => {
+                req.connection.destroy();
+            });
+
+            req.pipe(client_req);
+        });
     });
 
     return true;
 }
 
+// create a new tunnel with `id`
 function new_client(id, opt, cb) {
 
     // can't ask for id already is use
@@ -155,43 +181,49 @@ function new_client(id, opt, cb) {
         id = rand_id();
     }
 
-    var popt = {
+    const popt = {
         id: id,
         max_tcp_sockets: opt.max_tcp_sockets
     };
 
-    var client = Proxy(popt, function(err, info) {
-        if (err) {
-            return cb(err);
-        }
+    const client = Proxy(popt);
 
-        ++stats.tunnels;
-        clients[id] = client;
-
-        info.id = id;
-
-        cb(err, info);
-    });
+    // add to clients map immediately
+    // avoiding races with other clients requesting same id
+    clients[id] = client;
 
     client.on('end', function() {
         --stats.tunnels;
         delete clients[id];
     });
+
+    client.start((err, info) => {
+        if (err) {
+            delete clients[id];
+            cb(err);
+            return;
+        }
+
+        ++stats.tunnels;
+
+        info.id = id;
+        cb(err, info);
+    });
 }
 
 module.exports = function(opt) {
     opt = opt || {};
 
-    var schema = opt.secure ? 'https' : 'http';
+    const schema = opt.secure ? 'https' : 'http';
 
-    var app = express();
+    const app = express();
 
     app.get('/', function(req, res, next) {
         if (req.query['new'] === undefined) {
             return next();
         }
 
-        var req_id = rand_id();
+        const req_id = rand_id();
         debug('making new client with id %s', req_id);
         new_client(req_id, opt, function(err, info) {
             if (err) {
@@ -199,7 +231,7 @@ module.exports = function(opt) {
                 return res.end(err.message);
             }
 
-            var url = schema + '://' + req_id + '.' + req.headers.host;
+            const url = schema + '://' + req_id + '.' + req.headers.host;
             info.url = url;
             res.json(info);
         });
@@ -217,12 +249,18 @@ module.exports = function(opt) {
         proxy.web(req, res);
     });
 
+    app.get('/api/status', function(req, res, next) {
+        res.json({
+            tunnels: stats.tunnels,
+        });
+    });
+
     app.get('/:req_id', function(req, res, next) {
-        var req_id = req.params.req_id;
+        const req_id = req.params.req_id;
 
         // limit requested hostnames to 63 characters
         if (! /^[a-z0-9]{4,63}$/.test(req_id)) {
-            var err = new Error('Invalid subdomain. Subdomains must be lowercase and between 4 and 63 alphanumeric characters.');
+            const err = new Error('Invalid subdomain. Subdomains must be lowercase and between 4 and 63 alphanumeric characters.');
             err.statusCode = 403;
             return next(err);
         }
@@ -233,7 +271,7 @@ module.exports = function(opt) {
                 return next(err);
             }
 
-            var url = schema + '://' + req_id + '.' + req.headers.host;
+            const url = schema + '://' + req_id + '.' + req.headers.host;
             info.url = url;
             res.json(info);
         });
@@ -241,13 +279,13 @@ module.exports = function(opt) {
     });
 
     app.use(function(err, req, res, next) {
-        var status = err.statusCode || err.status || 500;
+        const status = err.statusCode || err.status || 500;
         res.status(status).json({
             message: err.message
         });
     });
 
-    var server = http.createServer();
+    const server = http.createServer();
 
     server.on('request', function(req, res) {
         debug('request %s', req.url);
diff --git a/test/mocha.opts b/test/mocha.opts
new file mode 100644
index 0000000..40f1956
--- /dev/null
+++ b/test/mocha.opts
@@ -0,0 +1,4 @@
+--check-leaks
+--reporter spec
+--ui qunit
+--compilers js:babel-register