lib/master.js
function startListening() {
    if (shouldBind) {
      try {
        bind(self.fd, self.port, self.host);
        listen(self.fd, self.options.backlog);
      } catch(e) {
        self.kill('SIGKILL');
        throw e;
      }
    }
    self.callback && self.callback();
    self.emit('listening');
  }
function startListening() {
    if (shouldBind) {
      try {
        bind(self.fd, self.port, self.host);
        listen(self.fd, self.options.backlog);
      } catch(e) {
        self.kill('SIGKILL');
        throw e;
      }
    }
    self.callback && self.callback();
    self.emit('listening');
  }
bind / listen