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TCP 3478

ProtocolTCP
Port3478
LabelsSTUN a protocol for NAT traversal

Synopsis

  • Port 3478/TCP is used by STUN and TURN servers for NAT traversal (e.g., RFC 5389 STUN and RFC 5766 TURN).
  • Microsoft Teams and Skype for Business connect to Microsoft Transport Relays over TCP 3478–3481 for STUN/TURN, using 3478/TCP when UDP is blocked.
  • Twilio’s Network Traversal Service (global.turn.twilio.com) exposes STUN/TURN on TCP 3478 for WebRTC applications.
  • Jitsi Meet and Matrix/Element deployments commonly run coturn on TCP 3478 to provide TURN relay service.
  • Amazon Chime and the Amazon Chime SDK require outbound access to TCP 3478 to reach AWS TURN servers for media relay.
  • Pexip Infinity and many Poly/Polycom video endpoints use TCP 3478 to communicate with TURN services when traversing restrictive networks.
  • Asterisk and FreeSWITCH deployments typically use coturn (or rfc5766-turn-server) listening on TCP 3478 for TURN.
  • Cisco Expressway/VCS and various SIP/WebRTC SBCs can be configured to use TURN on TCP 3478 for media traversal.
  • Misconfigured “open” TURN servers on 3478 have been abused for reflection/amplification DDoS and as proxy relays.

Observed activity

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