netcat是一个简单的读写网络连接数据的unix工具，用tcp和udp协议-Netcat is a simple Unix utility which reads and writes data

across network connections, using TCP or UDP protocol.

It is designed to be a reliable "back-end" tool that can　　　

be used directly or easily driven by other programs and　　

scr ipts.　At the same time, it is a feature-rich network　　

debugging and exploration tool, since it can create almost　　

any kind of connection you would need and has several　　　　

interesting built-in capabilities.　Netcat, or "nc" as the

actual program is named, should have been supplied long ago

as another one of those cryptic but standard Unix tools.