link#

현재 열린 포트 검색 가능#

20 ~ 1,000 열린 포트 검색

$ nc -z -v 127.0.0.1 20-1000
nc: connectx to 127.0.0.1 port 20 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 21 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 22 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 23 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 24 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 25 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 26 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 27 (tcp) failed: Connection refused

UDP 연결을 설정#

nc -u host port

Examples#

https://linux.die.net/man/1/nc
Open a TCP connection to port 42 of host.example.com, using port 31337 as the source port, with a timeout of 5 seconds:

$ nc -p 31337 -w 5 host.example.com 42

Open a UDP connection to port 53 of host.example.com:

$ nc -u host.example.com 53

Open a TCP connection to port 42 of host.example.com using 10.1.2.3 as the IP for the local end of the connection:

$ nc -s 10.1.2.3 host.example.com 42

Create and listen on a Unix Domain Socket:

$ nc -lU /var/tmp/dsocket

Connect to port 42 of host.example.com via an HTTP proxy at 10.2.3.4, port 8080. This example could also be used by ssh(1); see the ProxyCommand directive in ssh_config(5) for more information.

$ nc -x10.2.3.4:8080 -Xconnect host.example.com 42