监听外部主机 

nc [-options] hostname port[s] [ports] ... 

监听本地主机 

nc -l -p port [options] [hostname] [port] 

options: 

-d detach from console, stealth mode 

-e prog inbound program to exec [dangerous!!] 

-g gateway source-routing hop point[s], up to 8 

-g num source-routing pointer: 4, 8, 12, ... 

-h this cruft 

-i secs delay interval for lines sent, ports scanned 

-l listen mode, for inbound connects 

-l listen harder, re-listen on socket close 

-n numeric-only ip addresses, no dns 

-o file hex dump of traffic 

-p port local port number 

-r randomize local and remote ports 

-s addr local source address 

-t answer telnet negotiation 

-u udp mode 

-v verbose [use twice to be more verbose] 

-w secs timeout for connects and final net reads 

-z zero-i/o mode [used for scanning] 

port numbers can be individual or ranges: m-n [inclusive]