Which protocol is most commonly used for secure communication between IoT devices over the internet?        

MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol optimized for use with low-bandwidth, high-latency, or unreliable networks, making it ideal for IoT applications. It uses a publish-subscribe model to facilitate efficient communication between IoT devices. MQTT is preferred in IoT due to its minimal overhead and support for intermittent connectivity. a) HTTP is not specifically designed for low-bandwidth scenarios and is heavier compared to MQTT. b) FTP is used for file transfer and is not suitable for real-time or lightweight communication in IoT. d) SMTP is a protocol for email transmission, not for IoT communication. e) SNMP is used for network management and monitoring, not for IoT communication.