Find all IPs available in a range:

[root@lnx01 ~]# nmap -sn 192.168.0.0/24

Scan on specific ports:

# nmap -sV -p 22,443 192.168.0.0/24

Which port is open

manu-opensuse:/ # nmap -sT -p- 192.168.x.xxx
Starting Nmap 7.92 ( https://nmap.org ) at 2023-02-25 18:16 CET
Nmap scan report for 192.168.x.xxx
Host is up (0.0018s latency).
Not shown: 65520 closed tcp ports (conn-refused)
PORT      STATE SERVICE
53/tcp    open  domain
80/tcp    open  http
443/tcp   open  https
...
MAC Address: 2x:xx:xx (aaaaa SAS)

Nmap done: 1 IP address (1 host up) scanned in 8.34 seconds

[root@lnx01 ~]# rpm -ql nmap-ncat
/usr/bin/nc
/usr/bin/ncat
...

Test a port which is listening

[root@lnx01 ~]# nc -v lnx02 80
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 10.10.10.213:80.

[root@lnx01 ~]# nc -v lnx02 22
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 10.10.10.214:22.
SSH-2.0-OpenSSH_7.4

Test a port which is not open

[root@lnx01 ~]# nc -v lnx02 3333
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: No route to host.

Test a port which is listening

[root@lnx01 ~]# telnet lnx02 80
Trying 10.10.10.213...
Connected to lnx02.
Escape character is '^]'.

Test a port which is not open

[root@lnx01 ~]# telnet lnx02 888
Trying...

Test all open ports

# nmap -A -T4 scanme.nmap.org

Nmap scan report for scanme.nmap.org (74.207.244.221)
Host is up (0.029s latency).
rDNS record for 74.207.244.221: li86-221.members.linode.com
Not shown: 995 closed ports
PORT     STATE    SERVICE     VERSION
22/tcp   open     ssh         OpenSSH 5.3p1 Debian 3ubuntu7 (protocol 2.0)
| ssh-hostkey: 1024 8d:60:f1:7c:ca:b7:3d:0a:d6:67:54:9d:69:d9:b9:dd (DSA)
|_2048 79:f8:09:ac:d4:e2:32:42:10:49:d3:bd:20:82:85:ec (RSA)
80/tcp   open     http        Apache httpd 2.2.14 ((Ubuntu))
|_http-title: Go ahead and ScanMe!
646/tcp  filtered ldp
1720/tcp filtered H.323/Q.931
9929/tcp open     nping-echo  Nping echo
Device type: general purpose
Running: Linux 2.6.X
OS CPE: cpe:/o:linux:linux_kernel:2.6.39
OS details: Linux 2.6.39
Network Distance: 11 hops
Service Info: OS: Linux; CPE: cpe:/o:linux:kernel

TRACEROUTE (using port 53/tcp)
HOP RTT      ADDRESS
[Cut first 10 hops for brevity]
11  17.65 ms li86-221.members.linode.com (74.207.244.221)

Nmap done: 1 IP address (1 host up) scanned in 14.40 seconds

If you only want to know if the port is open, simply use:

# nc -vz www.microsoft.com 80

You can also use netcat to verify if UDP ports are open:

# nc -vz -u 8.8.8.8 53

And netcat can be used as a port scanner:

# nc -vz <hostname or ip address> 1-1000