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