MQTT is a handy protocol for sending/receiving lightweight data.

What is MQTT

MQTT stands for MQ Telemetry Transport. It is a publish/subscribe, extremely simple and lightweight messaging protocol, designed for constrained devices and low-bandwidth, high-latency or unreliable networks. The design principles are to minimise network bandwidth and device resource requirements whilst also attempting to ensure reliability and some degree of assurance of delivery. These principles also turn out to make the protocol ideal of the emerging “machine-to-machine” (M2M) or “Internet of Things” world of connected devices, and for mobile applications where bandwidth and battery power are at a premium.

V5.0 and v3.1.1 are OASIS standards (v3.1.1 is also a standard for ISO)

Protocol

The standard ports for MQTT to use.

TCP/IP port 1883 is reserved with IANA for use with MQTT.
TCP/IP port 8883 is also registered, for using MQTT over SSL.

What security does MQTT support.

You can pass a user name and password with an MQTT packet in V3.1 of the protocol. Encryption across the network can be handled with SSL, independently of the MQTT protocol itself (it is worth noting that SSL is not the lightest of protocols, and does add significant network overhead). Additional security can be added by an application encrypting data that it sends and receives, but this is not something built-in to the protocol, in order to keep it simple and lightweight.