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UDP 37

ProtocolUDP
Port37
Labelstime timserver

Synopsis

  • UDP port 37 is used by the RFC 868 Time Protocol.
  • Many Unix-like systems historically provided it via inetd/xinetd as the “time-udp” service (e.g., FreeBSD and Solaris inetd, and Linux via openbsd-inetd or xinetd).
  • Microsoft Windows Server’s optional “Simple TCP/IP Services” feature includes the Time service on UDP/37.
  • BusyBox rdate (commonly used in OpenWrt and other embedded systems) can query time over UDP/37 with the -u option.
  • HP TCP/IP Services for OpenVMS (UCX) includes an RFC 868 TIME server listening on UDP/37.
  • Security note: Open UDP/37 services have been abused for UDP reflection in DDoS attacks and are often targeted by scans, so most platforms disable it by default today.

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