coturn

coturn is an open-source TURN and STUN server implementation. It enables real-time communication applications to traverse NAT and firewalls by relaying media when direct peer-to-peer connections are not feasible. The software is used with VoIP, video conferencing, and WebRTC workloads to establish and maintain media paths between endpoints.

The project implements the TURN (Traversal Using Relays around NAT) and STUN (Session Traversal Utilities for NAT) protocols, allowing it to function as a STUN server, a TURN server, or a combined STUN/TURN relay. It supports multiple transport protocols, including UDP, TCP, TLS, and DTLS, and can listen on multiple interfaces and ports, with support for IPv4 and IPv6.

coturn is widely employed to enable reliable media sessions in environments with restrictive networks. It relies on authentication mechanisms based on long-term credentials, and can be configured to use a user database or static credentials. The software includes administrative tools for user management and configuration, enabling operators to control access and relay behavior through a comprehensive configuration file and command-line utilities.

Released under an open-source BSD-style license, coturn is cross-platform and widely used on Linux servers, though it has been ported to other operating systems. Deployment typically involves securing TURN/TLS traffic, controlling relay resources, and integrating coturn with application backends such as WebRTC gateways or SIP servers.