lsof
list of open files
lsof -i -P -n | grep LISTEN
netstat
Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
netstat -tulpn | grep LISTEN
ss
utility to investigate sockets
ss -tulpn | grep LISTEN
nmap
network exploration tool, port scanner
nmap -open 192.168.3.34
scanning open ports on remote IP address
nc -zv 192.168.3.34 2>&1 1-1024 | grep -v refused
this scans open ports in the range of 1 to 1024 on the above IP address.
redirects the error output to standard outoput and matches all lines except refused
scanning all open ports on the subnet using nmap
nmap -n 192.168.3.0/24
Sources
- Linux for Networking Professionals by Rob VandenBrink
- https://www.cyberciti.biz/faq/unix-linux-check-if-port-is-in-use-command/
- man pages
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