Client-Server Communication Protocols for Mobile

The internet is a global network of interconnected devices, including smartphones, tablets, and back-end servers, enabling communication and data exchange using standardized protocols like TCP/IP. Mobile applications interact with back-end servers ,and cloud services over the internet using protocols such as HTTP and HTTPS.

In mobile systems, the mobile apps’ devices act as clients, while back-end servers provide services and data. The mobile clients request the servers, which respond based on the application’s logic and user requirements. This communication between mobile clients and servers is typically carried out via APIs, with commonly used communication technologies such as HTTP, RPC, and WebSocket.

We’ll start by exploring the HTTP protocol, which is the foundation of most mobile app communication. RPC and WebSocket protocols are also important for specific mobile use cases, such as real-time updates or service-to-service interactions.

Communication protocols in mobile apps

In mobile System Design, protocols for client-server communication ensure reliable data exchange, user interaction, and background synchronization. Mobile systems must handle challenges like intermittent connectivity, variable network latency, and limited device resources.

When a mobile app needs to communicate with a server, it initiates a request through its networking stack. This process typically involves:

• DNS resolution: The app’s network library automatically resolves the server’s domain name into an IP address using the device’s built-in DNS resolver.

• Establishing a TCP connection: Once the IP address is known, the app establishes a TCP connection to the server.

• TLS handshake: If using HTTPS (the standard for mobile apps), a TLS handshake ensures that communication is encrypted.

• HTTP request/response: The app sends HTTP requests (e.g., GET, POST) to the server and processes the server’s HTTP responses.

Note: This process is handled internally by the mobile platform’s networking APIs (such as NSURLSession on iOS, OkHttp or HttpURLConnection on Android), abstracting much of the complexity away from developers. Users do not manually trigger DNS lookups or TCP connections; they are hidden behind simple API calls within the app.

Thus, the flow of information between mobile apps and servers primarily relies on HTTP protocols, with mobile-optimized variations like HTTP/2 or gRPC commonly used for performance improvements.

Let’s explore how the HTTP protocol works and enables client and server communication.

Hypertext Transfer Protocol

The Hypertext Transfer Protocol (HTTP) is a stateless, application-layer protocol designed for distributed information systems. It forms the foundation of data communication between mobile applications and back-end servers. It is also considered the de facto standard for resource sharing in mobile app ecosystems.

Mobile apps and back-end servers must adhere to the message formats and transmission methods specified in the HTTP standards. When a mobile app needs to retrieve or send data, for example, fetching a user profile or posting a comment, the app internally creates an HTTP request, which the server processes and responds to with the requested data.

Note: In mobile systems, these HTTP interactions happen seamlessly in the background through networking libraries provided by the mobile platform (e.g., ...