You need to know which services and ports are accessible over the internet. Do not forget UDP protoco ! Check your top 10 udp open ports with online port scanning tools.
Nmap is one of the most used tools for port scanning. That's why we use Nmap for port scanning. Nmap has a wide variety of parameters and a lot of scripts to work on port scans.
UDP (User Datagram Protocol) is a protocol (same as TCP) that defines rules to communicate with other systems in a network. TCP and UDP are both communication protocols in the network layer. But they are different from each other. TCP is connection-oriented, UDP is not. TCP makes sure that the messages reach the destination, UDP doesn't. UDP is used by protocols such as DNS, DHCP, TFTP, SNMP, RIP, VOIP. Also it is faster than TCP.
We scan only top 10 UDP ports. If you want to scan the most used 10 TCP ports, we have another top 10 tcp port scanner for this. Here is top 10 UDP ports.
|123||Network Time Protocol (NTP)|
|631||Internet Printing Protocol (IPP)|
We can advice you a few to things to do for UDP ports