Port 5353 — mDNS
Quick reference for TCP/UDP port 5353, used by mDNS. Includes what the service does, security guidance and related ports.
What is port 5353?
Multicast DNS — Apple Bonjour, Avahi.
What port does mDNS use?
mDNS listens on port 5353 by default.
Is port 5353 open? How to check
Run one of these from your computer, replacing HOST with the IP address or domain you want to test.
nc -zvu HOST 5353
Test-NetConnection HOST -Port 5353
nmap -sU -p 5353 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 5353 (mDNS) 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.
Related ports
Frequently asked
What is port 5353 used for?+
Port 5353 is the standard TCP/UDP port for mDNS. Multicast DNS — Apple Bonjour, Avahi.
What port does mDNS use?+
mDNS listens on port 5353 by default.
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