STUN Servers

STUN (Session Traversal Utilities for NAT) is a protocol used to assist in the discovery of the public IP address of a device located behind a Network Address Translator (NAT). NATs are commonly used in home and office networks to allow multiple devices to share a single public IP address. While NATs improve security, they can make it difficult for devices behind the NAT to communicate with devices outside the network.

The STUN server acts as a mediator between the device and the outside world, allowing the device to communicate with other devices outside the NAT. When a device wants to communicate with another device outside the NAT, it sends a STUN request to the STUN server. The STUN server responds with the device’s public IP address and port number. The device can then use this information to communicate with the other device.

STUN servers can be either public or private. Public STUN servers are freely available on the internet and can be used by anyone. Private STUN servers, on the other hand, are maintained by companies or organizations for their own use. When using a STUN server, it is important to ensure that the server is reliable and secure. A compromised STUN server can be used to launch attacks on devices behind the NAT, so it is important to use a trusted and secure server.

In conclusion, STUN servers play an important role in enabling communication between devices behind NATs and devices outside the network. They help devices to discover their public IP address and other network information, allowing for direct communication between devices. Whether using a public or private STUN server, it is important to ensure that the server is reliable and secure to prevent potential security issues.

Here are a few examples of how STUN servers are used:

1. WebRTC (Web Real-Time Communication): WebRTC is a technology that enables real-time communication between web browsers without the need for plugins or software downloads. When using WebRTC, a STUN server is used to help devices discover their public IP address and port number so that they can communicate with other devices.
2. VoIP (Voice over Internet Protocol): VoIP is a technology that allows voice calls to be made over the internet. When using VoIP, a STUN server is used to help devices behind a NAT discover their public IP address and port number so that they can receive incoming calls.
3. Online gaming: Online gaming often requires real-time communication between players. When playing games online, a STUN server can be used to help players discover their public IP address and port number so that they can communicate with other players.
4. Video conferencing: Video conferencing software allows users to have virtual meetings and conversations. When using video conferencing software, a STUN server is used to help participants discover their public IP address and port number so that they can communicate with other participants.
5. Remote desktop software: Remote desktop software allows users to access their computer from a remote location. When using remote desktop software, a STUN server can be used to help users discover their public IP address and port number so that they can connect to their computer.

In all of these use cases, a STUN server plays an important role in enabling communication between devices behind NATs and devices outside the network. It helps devices discover their public IP address and port number, allowing for direct communication between devices.

There are many STUN servers available on the internet, both public and private. Here are some examples of public STUN servers that can be used:

stun.stunprotocol.org

stun.l.google.com:19302

stun1.voiceeclipse.net

stun2.voiceeclipse.net

stun3.voiceeclipse.net

stun4.voiceeclipse.net

stun.ekiga.net

stun.ideasip.com

stun.ipshka.com

stun.schlund.de

It is important to note that these public STUN servers may not always be reliable or secure. In some cases, it may be necessary to use a private STUN server for improved reliability and security. Additionally, some WebRTC applications and services may have their own STUN servers that are optimized for their particular use case. It is often a good idea to check with the documentation of the specific application or service being used to determine the recommended STUN server to use.

Here is an example of Video chat application built using WebRTC, Socket IO & Google STUN server, It’s open source