nmap is a network discovery tool and can be used to perform a port scan, among other things. For example:

$ nmap -Pn --top-ports 100 192.168.1.1

Starting Nmap 7.95 ( https://nmap.org ) at 2024-10-27 18:59 CET
Nmap scan report for 3eefad8135fb448caa291b6950802356.fritz.box (192.168.1.1)
Host is up (0.19s latency).
Not shown: 97 closed tcp ports (conn-refused)
PORT     STATE SERVICE
22/tcp   open  ssh
111/tcp  open  rpcbind
2049/tcp open  nfs

Nmap done: 1 IP address (1 host up) scanned in 0.02 seconds