Practice · Ports & Protocols: The A+ Port List
// PRACTICE
Ports & Protocols: The A+ Port List
Free play — replay as much as you like. XP is awarded on your first clean pass.
Port 445 runs SMB (Server Message Block) — the protocol Windows uses for file sharing, printer sharing, and domain services. It's one of 16 port-and-protocol pairs the CompTIA A+ Core 1 exam (220-1201) expects you to know cold, alongside familiar ones like port 80 for HTTP and port 443 for HTTPS, and less obvious pairs like DHCP's 67/68 split or the legacy NetBIOS block (137–139).
Below is the full list — port number, protocol, transport (TCP or UDP), and whether it's secure — followed by Port Match, a timed drill that tests whether you actually know the pairings, not just recognize them.
// CompTIA A+ port and protocol list
| Port(s) | Protocol | Transport | Secure? |
|---|---|---|---|
| 20/21 | FTP | TCP | No — use SFTP or FTPS |
| 22 | SSH / SFTP / SCP | TCP | Yes |
| 23 | Telnet | TCP | No — use SSH |
| 25 | SMTP | TCP | No (base form) |
| 53 | DNS | UDP (primarily), TCP | — |
| 67/68 | DHCP | UDP | — |
| 80 | HTTP | TCP | No — use HTTPS |
| 110 | POP3 | TCP | No (base form) |
| 137 | NetBIOS Name Service | UDP / TCP | Legacy |
| 138 | NetBIOS Datagram | UDP | Legacy |
| 139 | NetBIOS Session | TCP | Legacy |
| 143 | IMAP | TCP | No (base form) |
| 389 | LDAP | TCP | No — use LDAPS |
| 443 | HTTPS | TCP | Yes |
| 445 | SMB/CIFS | TCP | — |
| 3389 | RDP | TCP | Requires additional controls |
// FAQ
What port does SMB use?
SMB (Server Message Block, also called CIFS) uses TCP port 445. This is the modern protocol for Windows file sharing, printer sharing, and domain services — when you open a shared folder at \\server\share, you're using SMB over port 445.
Is port 445 the same as port 139?
No. Port 139 is the older NetBIOS Session Service that Windows file sharing used to ride on; port 445 is direct SMB, used by modern Windows networking. Both still show up on the CompTIA A+ exam, so know them as two distinct answers, not interchangeable ones.
What's the difference between FTP's port 20 and port 21?
FTP uses two TCP ports: 21 is the control channel (login, directory listings, transfer commands) and 20 is the data channel (the actual file bytes). Both run over TCP, and both are insecure — FTP sends credentials and file contents in plaintext, which is why SFTP (port 22, via SSH) or FTPS is used instead.
Why does DHCP use two ports, 67 and 68?
Port 67 is the DHCP server's port; port 68 is the client's. They're split because a client requesting an address doesn't have an IP yet — the broadcast goes to the server's port 67, and the server's reply goes to the client's port 68.
Which CompTIA A+ ports are insecure, and what replaces them?
Telnet (23) is replaced by SSH (22); FTP (20/21) by SFTP or FTPS; HTTP (80) by HTTPS (443); and LDAP (389) by LDAPS. POP3 (110), IMAP (143), and SMTP (25) also have encrypted variants, though those ports fall outside the CompTIA A+ assigned list.