eclipse-mosquitto/mosquitto

Eclipse Mosquitto is an open source server that implements the MQTT messaging protocol. MQTT is a lightweight system used to pass short messages between devices over a network. It is commonly used in smart home setups, industrial sensors, and other situations where many small devices need to send status updates or receive commands without a lot of overhead. One device (or program) publishes a message to a named channel called a topic, and any number of other devices that have subscribed to that topic receive the message. Mosquitto acts as the central broker in this system. It receives messages from publishers and routes them to the appropriate subscribers. It supports versions 3.1, 3.1.1, and 5.0 of the MQTT standard, and it can handle connections from many clients at once. A public test server run by the project is available at test.mosquitto.org if you want to experiment without setting up your own. The project includes more than just the broker. It also ships command-line tools for publishing messages and subscribing to topics, which makes it easy to test setups or send messages from scripts. A C and C++ client library is included for developers who want to connect their own applications to an MQTT broker. Additional utilities handle password management and broker administration. Installing from a binary package on most platforms will start the broker automatically. A basic startup requires no configuration, though connecting from other machines or enabling authentication requires a configuration file. The documentation covers available authentication methods, security settings, and the dynamic security plugin for more flexible access control. The project is part of the Eclipse IoT ecosystem.