code: function(bs, done) {
          /**
           * An extra port is not needed in snippet/server mode
           */
          if (bs.options.get("mode") !== "proxy") {
              return done();
          }
  
          /**
           * Web socket support is disabled by default
           */
          if (!bs.options.getIn(["proxy", "ws"])) {
              return done();
          }
  
          /**
           * Use 1 higher than server port by default...
           */
          var socketPort = bs.options.get("port") + 1;
  
          /**
           * Or use the user-defined socket.port option instead
           */
          if (bs.options.hasIn(["socket", "port"])) {
              socketPort = bs.options.getIn(["socket", "port"]);
          }
  
          utils.getPort(bs.options.get("listen", "localhost"), socketPort, null, function(err, port) {
              if (err) {
                  return utils.fail(true, err, bs.cb);
              }
              done(null, {
                  optionsIn: [
                      {
                          path: ["socket", "port"],
                          value: port
                      }
                  ]
              });
          });
      }
docs: If the running mode is proxy, we'll use a separate port
  for the Browsersync web-socket server. This is to eliminate any issues
  with trying to proxy web sockets through to the users server.
  @param bs
  @param done