Connect

app.use()

Utilize the given middleware handle to the given route,
defaulting to /. This "route" is the mount-point for the
middleware, when given a value other than / the middleware
is only effective when that segment is present in the request's
pathname.

For example if we were to mount a function at /admin, it would
be invoked on /admin, and /admin/settings, however it would
not be invoked for /, or /posts.

Examples

 var app = connect();
 app.use(connect.favicon());
 app.use(connect.logger());
 app.use(connect.static(__dirname + '/public'));

If we wanted to prefix static files with /public, we could
"mount" the static() middleware:

 app.use('/public', connect.static(__dirname + '/public'));

This api is chainable, so the following is valid:

 connect()
   .use(connect.favicon())
   .use(connect.logger())
   .use(connect.static(__dirname + '/public'))
   .listen(3000);

Source

app.use = function(route, fn){
  // default route to '/'
  if ('string' != typeof route) {
    fn = route;
    route = '/';
  }

  // wrap sub-apps
  if ('function' == typeof fn.handle) {
    var server = fn;
    fn.route = route;
    fn = function(req, res, next){
      server.handle(req, res, next);
    };
  }

  // wrap vanilla http.Servers
  if (fn instanceof http.Server) {
    fn = fn.listeners('request')[0];
  }

  // strip trailing slash
  if ('/' == route[route.length - 1]) {
    route = route.slice(0, -1);
  }

  // add the middleware
  debug('use %s %s', route || '/', fn.name || 'anonymous');
  this.stack.push({ route: route, handle: fn });

  return this;
};

app.handle()

Handle server requests, punting them down
the middleware stack.

Source

app.handle = function(req, res, out) {
  var stack = this.stack
    , fqdn = ~req.url.indexOf('://')
    , removed = ''
    , slashAdded = false
    , index = 0;

  function next(err) {
    var layer, path, status, c;

    if (slashAdded) {
      req.url = req.url.substr(1);
      slashAdded = false;
    }

    req.url = removed + req.url;
    req.originalUrl = req.originalUrl || req.url;
    removed = '';

    // next callback
    layer = stack[index++];

    // all done
    if (!layer || res.headerSent) {
      // delegate to parent
      if (out) return out(err);

      // unhandled error
      if (err) {
        // default to 500
        if (res.statusCode < 400) res.statusCode = 500;
        debug('default %s', res.statusCode);

        // respect err.status
        if (err.status) res.statusCode = err.status;

        // production gets a basic error message
        var msg = 'production' == env
          ? http.STATUS_CODES[res.statusCode]
          : err.stack || err.toString();

        // log to stderr in a non-test env
        if ('test' != env) console.error(err.stack || err.toString());
        if (res.headerSent) return req.socket.destroy();
        res.setHeader('Content-Type', 'text/plain');
        res.setHeader('Content-Length', Buffer.byteLength(msg));
        if ('HEAD' == req.method) return res.end();
        res.end(msg);
      } else {
        debug('default 404');
        res.statusCode = 404;
        res.setHeader('Content-Type', 'text/plain');
        if ('HEAD' == req.method) return res.end();
        res.end('Cannot ' + req.method + ' ' + utils.escape(req.originalUrl));
      }
      return;
    }

    try {
      path = utils.parseUrl(req).pathname;
      if (undefined == path) path = '/';

      // skip this layer if the route doesn't match.
      if (0 != path.toLowerCase().indexOf(layer.route)) return next(err);

      c = path[layer.route.length];
      if (c && '/' != c && '.' != c) return next(err);

      // Call the layer handler
      // Trim off the part of the url that matches the route
      removed = layer.route;
      req.url = req.url.substr(removed.length);

      // Ensure leading slash
      if (!fqdn && '/' != req.url[0]) {
        req.url = '/' + req.url;
        slashAdded = true;
      }

      debug('%s', layer.handle.name || 'anonymous');
      var arity = layer.handle.length;
      if (err) {
        if (arity === 4) {
          layer.handle(err, req, res, next);
        } else {
          next(err);
        }
      } else if (arity < 4) {
        layer.handle(req, res, next);
      } else {
        next();
      }
    } catch (e) {
      next(e);
    }
  }
  next();
};

app.listen()

Listen for connections.

This method takes the same arguments
as node's http.Server#listen().

HTTP and HTTPS

If you run your application both as HTTP
and HTTPS you may wrap them individually,
since your Connect "server" is really just
a JavaScript Function.

 var connect = require('connect')
   , http = require('http')
   , https = require('https');

 var app = connect();

 http.createServer(app).listen(80);
 https.createServer(options, app).listen(443);

Source

app.listen = function(){
  var server = http.createServer(this);
  return server.listen.apply(server, arguments);
};