Firebase Cloud Messaging vs MQTT: What are the differences?

Introduction

Firebase Cloud Messaging (FCM) and MQTT are both widely used messaging protocols in the field of real-time communication. While they serve similar purposes, there are key differences between the two that make them suitable for different use cases.

1. Payload Format: In Firebase Cloud Messaging, the payload format is limited to JSON, allowing for structured and nested data. On the other hand, MQTT supports various payload formats including JSON, plain text, and binary data, providing more flexibility in data representation.

2. Message Routing: FCM uses a topic-based model for message routing, where messages are sent to specific topics that clients can subscribe to. MQTT, on the other hand, uses a publish-subscribe model, where clients subscribe to specific topics and receive messages published on those topics. This subtle difference in message routing mechanisms can impact the architecture and scalability of the messaging system.

3. Persistence: FCM provides persistence for undelivered messages, meaning that if a device is offline at the time of message sending, the message will be stored and delivered when the device comes online. MQTT, on the other hand, does not provide built-in persistence, requiring additional implementation to handle offline messages.

4. Bidirectional Communication: MQTT enables bidirectional communication between clients and the server through the use of both publish and subscribe operations. This allows devices to both send and receive messages without the need for constant polling. FCM primarily focuses on server-to-client push notifications, with limited support for bidirectional communication.

5. Built-in Authentication and Authorization: Firebase Cloud Messaging provides built-in authentication and access control mechanisms, allowing for secure and controlled access to the messaging service. MQTT, in contrast, does not have these features built-in and requires additional implementation and integration with authentication systems.

6. Scalability and Performance: FCM is a cloud-based messaging service provided by Firebase, which offers high scalability and reliability. MQTT, being a lightweight messaging protocol, is designed to be highly efficient and suitable for resource-constrained devices. The choice between FCM and MQTT depends on the specific scalability and performance requirements of the application.

In summary, Firebase Cloud Messaging and MQTT differ in payload format, message routing, persistence, bidirectional communication, authentication, and scalability. The choice between the two depends on the specific needs of the application in terms of data representation, messaging architecture, offline message handling, bidirectional communication, security, and scalability.