In the modern era of mobile and web app development, real-time communication is no longer just a feature—it's an expectation. Whether it's a chat app, a collaborative platform, or a live sports scoreboard, delivering timely and efficient communication between client and server is crucial. Yet, with so many communication protocols available—such as HTTPS, WebSockets, and Server-Sent Events (SSE)— choosing among them can be challenging, as each protocol offers distinct strengths and limitations.
In this blog, we’ll explore these communication methods in depth. We’ll understand how each works, where they shine, and how to decide which is right for your Android or iOS app.
Why Communication Methods Matter in App Development
Imagine building a messaging app that only fetches new messages when a user manually refreshes the screen. Now compare that to an app where messages pop up in real-time, just like WhatsApp or Telegram. That difference is powered by communication protocols beneath the surface. Choosing the right one affects everything from user experience and performance to battery consumption and data costs.
1. HTTPS (Request-Response Communication)
HTTPS (HyperText Transfer Protocol Secure) is the most common protocol for client-server communication in mobile and web applications. It follows a request-response model, meaning the client initiates a request, and the server replies with a response. There is no persistent connection between them—each interaction starts fresh.
This method is ideal for data that does not change frequently or doesn’t require real-time updates. For example, requesting a user’s profile data, fetching product listings, or submitting a form are perfect candidates for HTTPS.
Scenario:
In an e-commerce app, when a user browses the product catalog or taps “view order details,” the app sends an HTTPS request to the backend API. The server then returns the necessary data. This ensures a stateless, secure, and battery-friendly communication mode.
Pros:
- Simple to implement
- Secure and widely supported
- Easy caching and retry strategies
- Often easy to scale with HTTP statelessness.
Cons:
- Not real-time
- Client must initiate every interaction
- Real-time communication requires polling, which can be inefficient.
Android Example using Retrofit:
@GET("user/profile")
suspend fun getUserProfile(): UserProfile
2. WebSockets (Bi-Directional Real-Time Communication)
WebSockets offer a persistent, full-duplex communication channel over a single TCP connection. After an initial HTTP handshake, the protocol is upgraded, allowing both the client and server to send data at any time without needing to re-establish the connection.
This makes WebSockets ideal for apps that require real-time, interactive features such as messaging, multiplayer games, collaborative editing, or stock trading dashboards.
Scenario
In a chat application, once a user logs in, a WebSocket connection is established. This connection stays open and allows the user to receive messages instantly without needing to poll the server. Likewise, when the user sends a message, it is pushed to the server and instantly relayed to the recipient.
Pros:
- True real-time communication
- Bi-directional: both client and server can initiate messages
- Lower overhead for continuous communication
Cons:
- More complex to implement and maintain
- Higher battery and resource usage if not managed well
Android Example using Retrofit:
val request = Request.Builder().url("wss://yourapp.com/socket").build()
val socket = client.newWebSocket(request, object : WebSocketListener() {
override fun onMessage(webSocket: WebSocket, text: String){
// Handle incoming message
}
}
3. Server-Sent Events (SSE) – One-Way Streaming from Server
Server-Sent Events (SSE) are designed for situations where data needs to flow continuously from the server to the client, but not vice versa. Unlike WebSockets, SSE is a one-way channel over HTTP/1.1 that allows the server to push updates to the client as they become available.
SSEs are especially useful in use cases like real-time dashboards, news tickers, or notifications where the client doesn’t need to send much data back to the server.
Scenario:
Consider a live sports app where the client needs real-time score updates but doesn’t need to send anything back. Using SSE, the server can push score changes immediately as they happen without needing the client to repeatedly ask for updates.
Pros:
- Lightweight and easier to implement than WebSockets
- Lower bandwidth than polling
- Built-in reconnection and retry mechanisms (handled by library)
- Streamed over standard HTTP (no upgrade needed)
Cons:
- Only one-way: server to client
- Limited mobile support (especially on iOS/Android)
- Requires third-party library for Android support
- Doesn’t work natively with HTTP/2 or WebSocket-based infrastructure
Implementing SSE in Android with okhttp-eventsource (Bonus)
Although Android does not natively support SSE, we can implement it using the okhttp-eventsource library. This library, built on top of OkHttp, simplifies managing long-lived SSE connections and handles reconnection, parsing, and event dispatch.
Add dependencies in your build.gradle:
dependencies {
implementation 'com.squareup.okhttp3.okhttp:4.9.0'
implementation 'com.launchdarkly:okhttp-eventsource:2.5.0'
}
Note: On Android and iOS, native SSE support is lacking. A custom implementation using long-lived HTTP requests is often required, or alternatives like Firebase Cloud Messaging (FCM) can be considered.
4. Comparative Summary
Here’s a simplified comparison to help distinguish between the three major communication types:
| Feature | HTTPS | WebSocket | Server-Sent Events (SSE) |
|---|---|---|---|
| Direction | Client → Server | Bi-directional | Server → Client |
| Real-time | No | ✅ Yes | ✅ Yes |
| Complexity | Low | Medium | Medium |
| Battery Usage | Efficient | Can be high | Moderate |
| Android/iOS Support | ✅ Native | ✅ via libraries | Manual workaround |
| Use Cases | API calls | Chat, games | Live news, stock feed |
5. When to Use What?
Choosing the right communication method depends on the nature of your app and user expectations.
| Scenario | Recommended Protocol |
|---|---|
| Fetching static API data | HTTPS |
| Real-time messaging/chat | WebSockets |
| Live score or news updates | SSE (or WebSocket) |
| Collaborative document editing | WebSockets |
| Push notifications on mobile | FCM (Firebase) |
| Scheduled background syncs | HTTPS + WorkManager (Android) |
6. Real-World Example Use Cases
1. Real-Time Chat App
A messaging platform like WhatsApp or Slack benefits from WebSockets, allowing fast, two-way communication where users can send and receive messages instantly.
2. Stock Market App
An app that streams stock prices and updates the UI live can use Server-Sent Events or WebSockets depending on whether the client needs to send requests.
3. IoT Device Monitoring
A dashboard that displays sensor data from IoT devices in real-time can use WebSockets for bidirectional control or SSE for unidirectional status feeds.
4. E-Commerce App
For order history, product lists, or address details, HTTPS works well. For order delivery updates, a background notification system (FCM) or SSE/WebSocket feed can enhance user experience.
Conclusion
There’s no single “best” protocol. HTTPS is great for traditional data fetches; WebSockets excel at real-time two-way communication; SSE suits simple server-to-client streaming—if mobile support allows. Thoughtful protocol selection is key to building performant, scalable, and user-friendly apps.
- Use HTTPS for traditional API calls and one-time data fetches.
- Use WebSockets when real-time, low-latency, two-way communication is essential.
- Use SSE for simple server-to-client updates in lightweight apps, while being mindful of mobile support limitations.
Understanding these protocols, their mechanics, and their trade-offs is critical for building scalable, performant, and user-friendly applications—whether on Android, iOS, or the web.