September 05, 2025

What is TURN and STUN Server?

Real-time communication on the web (such as video calls, VoIP, and conferencing) relies on NAT traversal to allow peers to connect even when they’re behind firewalls or NAT (Network Address Translation) devices. Two key technologies enabling this are STUN and TURN servers.

STUN (Session Traversal Utilities for NAT)

A STUN server helps a device behind a NAT discover its public IP address and the type of NAT/firewall it is behind.
- It is lightweight and primarily used in peer-to-peer (P2P) connections.
- Works best when both peers can establish a direct connection.
- Commonly used in WebRTC applications to negotiate connectivity.

In short: STUN is used to find the best direct path for peers to connect.

TURN (Traversal Using Relays around NAT)

A TURN server goes a step further. If a direct connection fails (e.g., due to strict NAT or firewall restrictions), the TURN server relays the media traffic between peers.
- Ensures connectivity in restrictive network environments.
- Provides reliability at the cost of higher bandwidth usage (since all traffic flows through the server).
- Often used as a fallback when STUN alone isn’t enough.

In short: TURN guarantees connectivity by acting as a relay.

Here are some widely used solutions in real-time communication setups:

  • Google STUN Servers
    Free and reliable for testing and lightweight use cases.

  • Coturn
    An open-source TURN/STUN server that is widely adopted.

    • Self-hosted, giving you full control.
    • Suitable for developers who want a do-it-yourself (DIY) option.
    • Requires operational effort to scale, secure, and maintain.

  • Turnix.io
    A production-ready, scalable, and managed TURN service.

    • Optimized for real-world use cases.
    • Designed for reliability, global availability, and performance.
    • Ideal if you want to avoid the complexity of running and scaling your own TURN infrastructure.

Summary

  • STUN = finds your public IP and enables direct peer-to-peer connections.
  • TURN = relays traffic when direct connection isn’t possible.
  • Coturn = solid open-source option for self-service.
  • Turnix.io = a scalable, managed solution ready for production workloads.
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