Port 13 — daytime
Quick reference for TCP/UDP port 13, used by daytime. Includes what the service does, security guidance and related ports.
What is port 13?
Daytime protocol returning the current date and time (RFC 867).
What port does daytime use?
daytime listens on port 13 by default.
Is port 13 open? How to check
Run one of these from your computer, replacing HOST with the IP address or domain you want to test.
nc -zv HOST 13
Test-NetConnection HOST -Port 13
nmap -p 13 HOST
A refused or timed-out connection means the port is closed or filtered by a firewall.
Security guidance
Medium risk — open with care
Port 13 (daytime) can safely face the internet if you keep the software up to date, restrict admin endpoints, and use TLS where possible. Audit who can reach it and watch your logs.
Frequently asked
What is port 13 used for?+
Port 13 is the standard TCP/UDP port for daytime. Daytime protocol returning the current date and time (RFC 867).
What port does daytime use?+
daytime listens on port 13 by default.
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