$ port & service reference
Well-known TCP and UDP ports and what normally runs on them. Items marked caution are services that should not be reachable from the internet without a good reason. Test whether a port on your own host is reachable with the port check.
About the ports tool
A searchable reference of well-known TCP and UDP ports: which service normally listens where, and which ones are risky to expose to the internet. Filter by number, service name or keyword, or show only TCP, only UDP or only the services that deserve caution.
How to read the results
A port number only suggests a service; anything can listen anywhere. Ports below 1024 are well-known and need privileges to bind on Unix systems. Services marked caution, such as RDP, SMB, Telnet and unauthenticated databases, are frequent targets and should sit behind a VPN or firewall rules.
FAQ
- What port does SSH use?
- TCP 22. HTTPS is TCP 443 (and UDP 443 for HTTP/3), HTTP is TCP 80, DNS is port 53, and RDP is TCP 3389.
- What is the difference between TCP and UDP ports?
- They are separate number spaces. TCP is connection-oriented and reliable; UDP is connectionless, used by DNS, NTP, VPNs and streaming.
- How do I check whether a port is open?
- Use the port check tool to test common TCP ports on a host you own.
- Is it safe to change a default port?
- It reduces noise from automated scans but is not security by itself; use strong authentication and keep the service patched.