통신 port 상태를 확인하는 방법

작성자 이경미 수정일 2022-12-16 10:59

들어가며

L4 장비 및 서로 다른 서버 간의 통신을 확인할 수 있습니다.

내용

제품을 구성할 때에는 각 서버 간의 접근이 가능한지 확인해야합니다.

대상 서버 간의 port 접근이 되는지 확인하는 방법은 아래와 같습니다.

PING (ICMP)

ping <Option> <대상 ip_address>

- 접속 성공

ping <Ip_Address>
PING 192.168.50.220 (192.168.50.220) 56(84) bytes of data.
64 bytes from 192.168.50.220: icmp_seq=1 ttl=64 time=0.617 ms
64 bytes from 192.168.50.220: icmp_seq=2 ttl=64 time=0.349 ms
64 bytes from 192.168.50.220: icmp_seq=3 ttl=64 time=0.295 ms

- 접속 실패

ping <Ip_Address>
PING 192.168.50.220 (192.168.50.220) 56(84) bytes of data.
. 응답없음.

Telnet

telnet <대상 ip_address> <port>

- 접속 성공

telnet <Ip_Address> <Port>
Trying <Ip_Address>...
Connected to <Ip_Address>.
Escape character is '^]'.
SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.1

- 접속 실패

telnet <Ip_Address> <Port>
Trying <Ip_Address>...
telnet: Unable to connect to remote host: Connection refused

NC (NetCat)

nc <대상 ip_address> <port>

- 접속 성공

nc <Ip_Address> <Port>
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to <Ip_Address>

- 접속 실패

nc <Ip_Address> <Port>
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: No route to host

Curl

curl -v telnet:/<대상 ip_address>:<port>

- 접속 성공

curl -v <Ip_Address>:<Port>
* About to connect() to <Ip_Address> port <Port> (#0)
*   Trying <Ip_Address>...
* Connected to <Ip_Address> (<Ip_Address>) port <Port> (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.29.0
> Host: <Ip_Address>
> Accept: */*
> 
< HTTP/1.1 404 Not Found
< Server: nginx/1.19.1
< Date: Thu, 22 Sep 2022 06:40:57 GMT
< Content-Type: text/plain; charset=utf-8
< Content-Length: 21
< Connection: keep-alive
< 
* Connection #0 to host <Ip_Address> left intact

- 접속 실패

curl -v <Ip_Address>:<Port>
* About to connect() to <Ip_Address> port <Port> (#0)
*   Trying <Ip_Address>...
* No route to host
* Failed connect to <Ip_Address>:<Port>; No route to host
* Closing connection 0
curl: (7) Failed connect to <Ip_Address>:<Port>; No route to host

Echo

echo /dev/tcp/<대상 ip_address>/<port>
echo $?

- 접속 성공

echo > /dev/tcp/<Ip_Address>/<Port>
echo $?
0

- 접속 실패

echo > /dev/tcp/<Ip_Address>/<Port>
bash: connect: 연결이 거부됨
bash: /dev/tcp/<Ip_Address>/<Port>: 연결이 거부됨
echo $?
1