telnet 외 서버 포트 체크하는 법

보안이슈로 인해 telent 포트를 사용하지 못할 경우 아래의 방법으로 대체하여 사용

 

 

1. nc (Netcat)

1) netcat 설치

# yum -y installl nc # apt install netcat

 

2) netcat 기본 옵션

# nc [옵션] [IP] [PORT] # nc --help -z \\ nc에 데이터를 보내지 않고 열린포트만 검색하도록 지시 -v \\ 자세한 정보 제공 -u \\ UDP 연결 설정

 

3) nc 사용 예제

IP는 x.x.x.x 로 표시하였음 # nc -zv x.x.x.x 80 \\ 80번 포트 검색 Connection to  x.x.x.x 80 port [tcp/http] succeeded! # nc -zv x.x.x.x 21-30 \\ 21번 ~ 30번 포트 범위를 설정하여 검색 nc: connect to x.x.x.x port 21 (tcp) failed: Connection refused Connection to x.x.x.x 22 port [tcp/ssh] succeeded! nc: connect to x.x.x.x port 23 (tcp) failed: No route to host nc: connect to x.x.x.x port 24 (tcp) failed: No route to host Connection to x.x.x.x 25 port [tcp/smtp] succeeded! nc: connect to x.x.x.x port 26 (tcp) failed: No route to host nc: connect to x.x.x.x port 27 (tcp) failed: No route to host nc: connect to x.x.x.x port 28 (tcp) failed: No route to host nc: connect to x.x.x.x port 29 (tcp) failed: No route to host nc: connect to x.x.x.x port 30 (tcp) failed: No route to host # nc -zv x.x.x.x 20-30 2>&1 |grep succeeded \\ 20-30번 포트 중 열린포트만 출력 Connection to x.x.x.x 22 port [tcp/ssh] succeeded! Connection to x.x.x.x 25 port [tcp/smtp] succeeded! # echo "EXIT" | nc x.x.x.x 22 \\ ssh 버전 확인  SSH-2.0-OpenSSH_7.4 Protocol mismatch.

 

 

2. curl

# curl-v [IP]:[PORT]