| 20 | TCP | File Transfer Protocol (FTP)—Data connection | Make files available for download across a network (data connection port) |
| 21 | TCP | File Transfer Protocol (FTP)—Control connection | Make files available for download across a network (control connection port) |
| 22 | TCP | Secure Shell (SSH) | Make a secure connection to the command-line interface of a server |
| 23 | TCP | Telnet | Make an unsecure connection to the command-line interface of a server |
| 25 | TCP | Simple Mail Transfer Protocol (SMTP) | Transfer email messages across a network |
| 53 | TCP/UDP | Domain Name System (DNS) | Facilitate identification of hosts by name alongside IP addressing |
| 67 | UDP | Dynamic Host Configuration Protocol (DHCP) Server | Provision an IP address configuration to clients |
| 68 | UDP | DHCP Client | Request a dynamic IP address configuration from a server |
| 80 | TCP | HyperText Transfer Protocol (HTTP) | Provision unsecure websites and web services |
| 110 | TCP | Post Office Protocol (POP) | Retrieve email messages from a server mailbox |
| 137-139 | UDP/TCP | NetBIOS over TCP/IP | Support networking features of legacy Windows versions |
| 143 | TCP | Internet Mail Access Protocol (IMAP) | Read and manage mail messages on a server mailbox |
| 161 | UDP | Simple Network Management Protocol (SNMP) | Query status information from network devices |
| 162 | UDP | SNMP trap operation | Report status information to a management server |
| 389 | TCP | Lightweight Directory Access Protocol (LDAP) | Query information about network users and resources |
| 443 | TCP | HTTP Secure (HTTPS) | Provision secure websites and services |
| 445 | TCP | Server Message Block (SMB) | Implement Windows-compatible file and printer sharing services on a local network (also sometimes referred to as Common Internet File System [CIFS]) |
| 3389 | TCP | Remote Desktop Protocol (RDP) | Make a secure connection to the graphical desktop of a computer |