MQTT_VPN | IP over MQTT for ESP controllers and Linux

MQTT_VPN is a C library typically used in Internet of Things (IoT) applications. MQTT_VPN has no bugs, it has no vulnerabilities and it has low support. You can download it from GitHub.

The idea of this project is to enable bidirectional IP connectivity, where it is not available otherwise, e.g. if one node is hidden behind (several layers of) NAT. This is the case in most private networks and also in mobile IP networks. Prerequisite is, that all connected nodes can reach a common MQTT broker. This allows you to "dial-in" into an IoT device sitting anywhere in the internet. On all connected clients it sets up a simple (optionally encrypted) IP network where all clients connected to the same MQTT broker can communicate with each other via IP (IPv6 is not yet working). IP is tunneled via MQTT. On the nodes it creates a TUN interface, assignes an IP address, and publishes all packets to an MQTT topic mqttip/[dest IP address]. At the same time it subscribes to an MQTT topic mqttip/[own IP address]. This establishes a fully connected IP network. "Switching" is done via the pub/sub mechanism of the MQTT broker.