A number of ports are safe to open such as the ones used for Internet access, email and FTP file transfers. Common port numbers that typically may be open include 21, 25, 80, 110, 139 and 8080. By default, these port numbers are usually active and open in most routers.
Czyli precyzując, najczęściej otwarte standardowo są te porty.
- 21, 25, 80, 110, 139 oraz 8080
A co do drugiego pytania, to z jakiego systemu kolega korzysta?
- Pod Linux jest to nmap i netstat, lsof, ss
- Pod Windows polecam zajrzeć TUTAJ
Pozdrawiam!