Port 3478 (STUN / TURN)

STUN and TURN for WebRTC, video calls and games to find public addresses and relay media through NAT (coturn).

Registered (user) port, 1024-49151 UDPTCP Voice, video and chat Meant to face the internet

What port 3478 is used for

STUN and TURN for WebRTC, video calls and games to find public addresses and relay media through NAT (coturn).

Security: should port 3478 be open?

Meant to face the internet. A TURN server needs to be public, but require credentials and deny relaying to private and loopback addresses (denied-peer-ip), or attackers can use it to reach your internal network.

IANA assignment

Service nameProtoDescriptionAssigneeReference

stun TCP Session Traversal Utilities for NAT (STUN) port IESG RFC 8489

turn TCP TURN over TCP - RFC 8656

stun-behavior TCP STUN Behavior Discovery over TCP - RFC 5780

stun UDP Session Traversal Utilities for NAT (STUN) port IESG RFC 8489

turn UDP TURN over UDP - RFC 8656

stun-behavior UDP STUN Behavior Discovery over UDP - RFC 5780

Registry dates for this port: last modified 2019-08-02.

Check what is listening on port 3478

Linux: is anything listening on TCP 3478?

sudo ss -tlnp 'sport = :3478'

Linux: UDP 3478

sudo ss -ulnp 'sport = :3478'

Linux / macOS: which process owns the port

sudo lsof -nP -i :3478

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':3478 '

Windows (Command Prompt)

netstat -ano | findstr :3478

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3478 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 3478

From Windows

Test-NetConnection HOST -Port 3478

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 3478

Open port 3478 in the firewall

ufw

sudo ufw allow 3478/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 3478 -j ACCEPT

nftables

sudo nft add rule inet filter input tcp dport 3478 accept

Windows Firewall

New-NetFirewallRule -DisplayName 'Allow TCP 3478' -Direction Inbound -Protocol TCP -LocalPort 3478 -Action Allow

ufw

sudo ufw allow 3478/udp