Port Number Quiz — well-known TCP/UDP ports practice (66 ports)
Learn common TCP/UDP port numbers with a 10-question timed quiz: port → service, service → port or mixed, three difficulty pools from 15 essentials to 66 ports, explanations, personal bests and a shareable challenge link.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
Ports 0–1023 are the well-known range, 1024–49151 are registered, and 49152–65535 are dynamic. Firewall rules, ACLs and packet captures are much quicker to read once the common ones are automatic.
About this tool
This port number quiz helps you learn the TCP and UDP ports that show up in firewall rules, ACLs, packet captures and certification exams. Each round is ten timed multiple-choice questions — port to service, service to port, or a mix — drawn from 15 essentials, 35 everyday ports or all 66, from SSH and DNS to RADIUS, IPsec NAT-T, MQTT and WireGuard. Answer with a click or the keys 1–4; every answer shows the port, its protocol and service, and services that only use a port by convention are labelled as such. Your best score is kept in this browser, and the share link sends friends the exact same questions. Everything runs in your browser.
Frequently asked questions
Which port numbers should I memorise first?
The fifteen in Easy mode cover most real-world traffic: 22 SSH, 23 Telnet, 21 FTP, 25 SMTP, 53 DNS, 67 DHCP, 69 TFTP, 80 HTTP, 443 HTTPS, 110 POP3, 143 IMAP, 123 NTP, 161 SNMP, 445 SMB and 3389 RDP. Once those are instant, move to Normal, which adds the secure mail ports, LDAP, Kerberos, syslog, databases and the routing and VPN basics that network exams like to ask about.
What are well-known, registered and dynamic ports?
IANA splits the 65,536 ports into three ranges. 0–1023 are well-known ports for core services, and on Unix-like systems binding to them traditionally needs root. 1024–49151 are registered ports, assigned to applications on request, such as 3306 for MySQL. 49152–65535 are dynamic or private ports, used as temporary source ports for outgoing connections. Operating systems pick their own ephemeral range — Windows follows IANA, while Linux defaults to 32768–60999 — which matters when writing return-traffic firewall rules.
Why do some services have more than one port?
Usually because of roles or encryption. FTP uses 21 for control and 20 for active-mode data; DHCP servers listen on 67 and clients on 68. Mail splits by job: 25 is server-to-server SMTP, 587 is client submission upgraded with STARTTLS, and 465 is submission with TLS from the first byte; IMAP 143 and POP3 110 likewise have TLS-only siblings 993 and 995, and LDAP 389 has 636. RADIUS separates authentication (1812) from accounting (1813), and SNMP sends traps to 162 rather than 161.
Which common services use UDP instead of TCP?
Services that send short request–response messages or need low latency: DHCP (67/68), TFTP (69), NTP (123), SNMP (161/162), syslog (514), IKE (500) and IPsec NAT-T (4500), RADIUS (1812/1813), RIP (520), mDNS (5353), and VPNs such as OpenVPN and WireGuard by default. DNS uses both — UDP 53 for ordinary queries, TCP 53 for zone transfers and responses too large for UDP — which is why blocking TCP 53 breaks DNS in subtle ways. The quiz shows the protocol in every question.
Does changing a service's port make it more secure?
Only marginally. Moving SSH off 22 cuts down noisy automated login attempts in the logs, but any port scan finds the service in seconds, so it is not a control by itself — keys, MFA, patching and firewall rules that limit who can connect are what protect it. Port numbers are conventions, not rules: anything can run on any port, which is why modern firewalls identify applications rather than trusting the number. Some defaults in this quiz, such as 6443 for Kubernetes, 27017 for MongoDB and 51820 for WireGuard, are conventions rather than IANA assignments and are marked as such.