telnet – только TCP
$ telnet 77.77.77.77 5060
nmap скачать: https://nmap.org/download.html
# порт 10081 TCP
nmap -p 10081 srv
Nmap scan report for srv (192.168.1.11)
rDNS record for 192.168.1.11: srv
PORT STATE SERVICE
10081/tcp open unknown
# порт 5060 UDP
$ nmap -sU -p U:5060 77.77.77.77
Nmap scan report for asterisk.domain.com (77.77.77.77)
PORT STATE SERVICE
5060/udp open|filtered sip