How to ping and test for a specific port from Linux or Unix command line
I
wanted to see if a specific port of a desktop computer or server is open from a Linux or Unix command line shell. How do I ping a specific port? Is it possible possible to ping an 192.168.1.254:80 or 192.168.1.254:23 ports?
You use the ping command to send ICMP ECHO_REQUEST packets to network computers, routers, switches and more. ping works with both IPv4 and IPv6. Ping is using ICMP protcol. The ping command can not be used to ping a specific port.
However, use any one of the following command to see if a port is open or not as follows:
Use telnet command
The syntax is:
telnet {host} {port}
telnet www.cyberciti.biz 80
telnet 192.168.2.254 80
Sample outputs:
Trying 192.168.2.254…
Connected to router.
Escape character is ^] .
^]
telnet> q
Connection closed.
To close your session, press Ctrl+]+q.
Use nc command
The syntax is:
nc -vz {host} {port}
nc -vz 192.168.2.254 80
nc -vz www.cyberciti.biz 443
Sample outputs:
found 0 associations
found 1 connections:
1: flags=82
outif utun1
src 10.8.0.2 port 54997
dst 104.20.187.5 port 443
rank info not available
TCP aux info available
Connection to www.cyberciti.biz port 443 [tcp/https] succeeded!
Use nmap command
The syntax is:
nmap -PNp {port} {host}
nmap -p {port} {host}
nmap -p 22 www.cyberciti.biz
nmap -p 443 192.168.2.254
Sample outputs:
Starting Nmap 7.40 ( https://nmap.org ) at 2017-05-24 01:00 IST
Nmap scan report for router (192.168.2.254)
Host is up (0.00034s latency).
PORT STATE SERVICE
443/tcp open https
Nmap done: 1 IP address (1 host up) scanned in 0.04 seconds
See “Top 32 Nmap Command Examples For Sys/Network Admins” for more info.
Use bash shell
The syntax is as follows:
check for tcp port ##
need bash shell ##
(echo >/dev/tcp/{host}/{port}) &>/dev/null && echo open || echo close
(echo >/dev/udp/{host}/{port}) &>/dev/null && echo open || echo close
(echo >/dev/tcp/www.cyberciti.biz/22) &>/dev/null && echo Open 22 || echo Close 22
(echo >/dev/tcp/www.cyberciti.biz/443) &>/dev/null && echo Open 443 || echo Close 443
Sample outputs:
Close 22
Open 443
Use nping command
Nping is an open-source tool for network packet generation, response analysis and response time measurement. Nping allows users to generate network packets of a wide range of protocols, letting them tunevirtually any field of the protocol headers. While Nping can be used as a simple ping utility to detect active hosts, it can also be used as a raw packet generator. The syntax is:
sudo nping –tcp -p {port} {host}
sudo nping –tcp -p 443 www.cyberciti.biz
Sample outputs:
Fig.01: nping just pinged www.cyberciti.biz host at port 443
