Common Ports and Services

Protocol & Port Service
TCP 22 / 23 Secure Shell / Telnet
TCP 3389 Microsoft Remote Desktop
TCP 5900 Virtual Network Computing (VNC)
TCP 445 Microsoft Networking & Interprocess Communications
TCP 80 /(443) Hypertext Transfer Protocol (Secure) (HTTP & HTTPS)
Protocol & Port Service
TCP 25 Simple Mail Transfer Protocol (SMTP)
UDP 53 DNS Requests
TCP 110,995 Post Office Protocol 3 (S) - to retrieve or check email
TCP 143,993 Internet Message Access Protocol (S) - retrieving
TCP 135,137,139 Older Microsoft services
TCP 21 File Transfer Protocol (FTP)

Nmap