操作系统提供的 connect() 系统调用，用来与每一个感兴趣的目标计算机的端口进行连接。如果端口处于侦听状态，那么connect()就能成功。否则，这个端口是不能用的，即没有提供服务。这个技术的一个最大的优点是，你不需要任何权限。系统中的任何用户都有权利使用这个调用。另一个好处就是速度。如果对每个目标端口以线性的方式，使用单独的connect()调用，那么将会花费相当长的时间，你可以通过同时打开多个套接字，从而加速扫描。使用非阻塞 I/O 允许你设置一个低的时间用尽周期，同时观察多个套接字。但这种方法的缺点是很容易被发觉，并且被过滤掉。目标计算机的logs文件会显示一连串的连接和连接是出错的服务消息，并且能很快的使它关闭。

-operating system for the connect () system call, and for every one interested in the computer connect to the port. If the interception at the state port, then connect () can be successful. Otherwise, the port is not used, that is, not provide services. One of the biggest advantages is that you do not have any authority. System of any user has the right to use this call. Another advantage is speed. If each of the target port to a linear manner, the use of separate connect () call, it would take a very long time, you can open multiple socket, thus speeding up the scanning. The use of non-blocking I / O allows you to set up a low exhaustion of the time cycle, while observing a number of sockets. But the shortcomings of this method is very easy to be found, and to filter out. The computer logs