Port 37: Time Protocol
Port 37 is the Time Protocol, an early way for a client to fetch the current time from a server as a raw count of seconds since 1900. NTP on port 123 replaced it for anything that needs real accuracy.
TCP/UDPLegacy protocolsUnencrypted by defaultIANA assigned
| Port number | 37 |
|---|---|
| Service | Time Protocol |
| Protocol | TCP/UDP |
| Category | Legacy protocols |
| Default encryption | No |
Security note. Port 37 is not encrypted by default. Restrict it to trusted networks, or use an encrypted alternative where one exists, to avoid exposing credentials and data in transit.
Frequently asked questions
What is port 37 used for?
Port 37 is the Time Protocol, an early way for a client to fetch the current time from a server as a raw count of seconds since 1900. NTP on port 123 replaced it for anything that needs real accuracy.
Is port 37 TCP or UDP?
Port 37 (Time Protocol) uses TCP/UDP.
Is port 37 secure?
Port 37 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 37 on my firewall?
Only if you specifically need Time Protocol. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.