Free study tool
Port and protocol reference
The well-known TCP and UDP ports that come up on CompTIA A+ and CompTIA Network+, each linked to its entry in the IANA service name and port registry. Filter the table, then quiz yourself.
Useful for CompTIA A+ Core 1 and CompTIA Network+
28 ports
Quiz yourself
Reading the table
The transport column shows what each protocol uses on that port in practice. IANA often registers a service on both TCP and UDP even when only one is used, so the registry entry can list more than the table does.
Some protocols need more than one port. FTP uses 21 for its control connection and 20 for data, DHCP servers listen on 67 while clients use 68, and SNMP agents answer on 161 while traps go to 162.
SFTP has no port of its own in this list: it runs inside SSH on port 22. The sftp name IANA registers on port 115 belongs to an older, unrelated protocol.
Common questions
- What port does DNS use?
- Port 53, over both UDP and TCP.
- What ports does DHCP use?
- UDP 67 for the server and UDP 68 for the client. Clients send to the server on 67, and servers reply to clients on 68.
- Which ports are the secure versions of common protocols?
- HTTPS uses TCP 443 instead of HTTP's 80, LDAPS uses TCP 636 instead of LDAP's 389, and SIP over TLS uses TCP 5061 instead of 5060. SSH on TCP 22 replaces Telnet on 23.
- What port does Remote Desktop use?
- TCP 3389, registered with IANA as ms-wbt-server.
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