Implement the MQTT Protocol for IoT Messaging

Write a C program that builds MQTT CONNECT and PUBLISH packets. Show the packet bytes and a field breakdown.

Requirements:

• Define the MQTT fixed header structure with packet type and remaining length
• Build a CONNECT packet with protocol name (MQTT), protocol level (4), connect flags, and keep alive
• Include a client ID in the CONNECT payload
• Encode the remaining length using MQTT variable-length encoding
• Build a PUBLISH packet with topic name and message payload
• Print the raw bytes of both packets in hexadecimal
• Print a breakdown of each field (type, flags, remaining length, variable header, payload)
• Show the packet structure with clear printf labels