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UDP 3478

ProtocolUDP
Port3478
LabelsSTUN a protocol for NAT traversal

Synopsis

  • UDP port 3478 is used by the STUN/TURN protocols for NAT traversal in real-time communications.
  • Microsoft Teams and Skype for Business/Lync use UDP 3478–3481 to reach Microsoft’s STUN/TURN (Edge) services for audio/video connectivity.
  • Zoom clients use UDP 3478 (and 3479) to Zoom’s STUN infrastructure for connectivity checks and ICE.
  • Cisco Webex applications use UDP 3478 to access Webex-hosted STUN/TURN services for media traversal.
  • Twilio’s STUN/TURN endpoints (e.g., global.stun.twilio.com and turn.twilio.com) listen on UDP 3478 for WebRTC applications.
  • The coturn TURN server (commonly deployed with Jitsi Meet, Nextcloud Talk, and Matrix/Element) defaults to UDP 3478 for STUN/TURN.
  • Discord and many other WebRTC-based apps often reach third-party or self-hosted coturn servers on UDP 3478 for ICE.
  • Security note: Open STUN/TURN servers on UDP 3478 have been abused in reflection/amplification DDoS attacks when misconfigured or publicly exposed.

Observed activity

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