Differences Between WebSocket and HTTP Communication, Usage Scenarios, and WebSocket Code Examples

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There is a surprise at the bottom of the article!!!✅ 1. What is WebSocket?

WebSocket is a protocol forfull-duplex communication over a single TCP connection.

It establishes a persistent connection through a “protocol upgrade” on top of the traditional HTTP protocol, allowing the client and server to actively send data to each other, no longer limited to the request-response model.

The WebSocket protocol is defined by the IETF (RFC 6455) and the WebSocket API is standardized by the W3C.

✅ 2. WebSocket Communication Mechanism

🔹 1. Establishing Connection (Handshake)

The initial connection is established through an HTTP request;
The client sends the Upgrade: websocket request header;
The server returns 101 Switching Protocols indicating that the protocol upgrade was successful.

🔹 2. Bidirectional Communication

After the handshake is successful, both the client and server can actively send messages;
Messages are transmitted in the form of “frames”, supporting text and binary formats.

🔹 3. Maintaining Connection

The connection is a persistent connection;
Supports a heartbeat mechanism (Ping/Pong frames) to maintain activity.

Summary of Features

Lightweight: Based on the Java-WebSocket library, suitable for client, desktop applications, or intermediate service calls.
Event-Driven: Based on callback handling, naturally suitable for asynchronous message models.
Supports SSL, proxies, and custom headers: Adaptable to complex deployment environments.
Applicable Scenarios: Online monitoring, chat, push clients, crawlers, and real-time data reception.

✅ 3. Differences Between WebSocket and HTTP

Comparison Dimension	HTTP Communication	WebSocket Communication
Protocol	Request/Response protocol based on TCP (stateless)	Full-duplex protocol based on TCP
Connection Method	Client requests once, server responds once	Establishes a persistent connection with one handshake, allowing bidirectional communication thereafter
Status Management	Stateless (client needs to pass identity)	Stateful connection (can maintain session in memory)
Data Transmission	Each communication requires the full HTTP header	Small data frames, high transmission efficiency
Server Push	Not supported (requires polling or long polling)	Natively supports server push
Performance	High connection overhead, high latency	Strong real-time performance, low resource consumption
Application Layer Protocol	Explicit: HTTP/1.1, HTTP/2	After protocol upgrade, it is WS or WSS (encrypted)

✅ 4. Usage Scenarios for Each

🔹 Scenarios More Suitable for HTTP:

Regular request/response, such as page loading, form submission, file uploads, etc.;
RESTful API services;
Business systems with low-frequency interactions or infrequent data changes.

🔹 Scenarios More Suitable for WebSocket:

Real-time systems, such as IM chat, online games, collaborative office, stock market push;
Business scenarios where the server needs to actively push messages;
High concurrency and low latency communication scenarios (e.g., issuing commands to IoT devices).

✅ 5. How to Choose Between WebSocket and HTTP?

Is there a need for real-time communication between front-end and back-end?

If yes: WebSocket is more suitable.

Is the data transmission frequency high?

High-frequency push: WebSocket.

Is bidirectional communication needed?

For real-time feedback or control (e.g., IoT, IM): WebSocket.

Is there a need for the server to actively send messages?

If yes: WebSocket.

✅ 6. WebSocket Usage Example (Based on Java + Spring Boot) 1. Introduce dependencies

<dependency>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-websocket</artifactId></dependency>

2. Create WebSocket Configuration Class

@Configuration@EnableWebSocketpublic class WebSocketConfig implements WebSocketConfigurer {    @Override    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {        registry.addHandler(new MyWebSocketHandler(), "/ws")                .setAllowedOrigins("*"); // Allow cross-origin    }}

3. Write Handler Logic

public class MyWebSocketHandler extends TextWebSocketHandler {    private static final Map<String, WebSocketSession> sessions = new ConcurrentHashMap<>();    @Override    public void afterConnectionEstablished(WebSocketSession session) {        String userId = Objects.requireNonNull(session.getUri()).getQuery(); // Can get user ID from parameters        sessions.put(userId, session);        System.out.println("Connection established: " + userId);    }    @Override    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws IOException {        System.out.println("Received message: " + message.getPayload());        session.sendMessage(new TextMessage("Received: " + message.getPayload()));    }    @Override    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) {        sessions.values().remove(session);        System.out.println("Connection closed");    }    public void sendToUser(String userId, String msg) throws IOException {        WebSocketSession session = sessions.get(userId);        if (session != null && session.isOpen()) {            session.sendMessage(new TextMessage(msg));        }    }}

4. Client Code (HTML Example)Java code can also be used to establish the connection

<script>    const socket = new WebSocket("ws://localhost:8080/ws?userId=zheng");    socket.onopen = function() {        console.log("Connection successful");        socket.send("Hello, server");    };    socket.onmessage = function(event) {        console.log("Received message: " + event.data);    };    socket.onclose = function() {        console.log("Connection closed");    };</script>

5. Java as ClientMaven Dependency

<dependency>    <groupId>org.java-websocket</groupId>    <artifactId>Java-WebSocket</artifactId>    <version>1.5.3</version></dependency>

Code Example: Basic Connection Demo

import org.java_websocket.client.WebSocketClient;import org.java_websocket.handshake.ServerHandshake;import java.net.URI;public class MyWebSocketClient extends WebSocketClient {    public MyWebSocketClient(URI serverUri) {        super(serverUri);    }    @Override    public void onOpen(ServerHandshake handshakedata) {        System.out.println("Connection successful");        send("Hello, server!");    }    @Override    public void onMessage(String message) {        System.out.println("Received message: " + message);    }    @Override    public void onClose(int code, String reason, boolean remote) {        System.out.println("Connection closed, code=" + code + ", reason=" + reason + ", remote=" + remote);    }    @Override    public void onError(Exception ex) {        System.err.println("Error occurred: " + ex.getMessage());    }    public static void main(String[] args) throws Exception {        URI serverUri = new URI("ws://localhost:8080/ws?userId=123");        MyWebSocketClient client = new MyWebSocketClient(serverUri);        client.connect();    }}

Core Class Description

Class / Method	Description
WebSocketClient	Abstract class that encapsulates WebSocket protocol handling logic, requires a custom subclass to implement event responses.
onOpen(ServerHandshake)	Triggered when the connection is successfully established, can send authentication information or initialization commands.
onMessage(String message)	Receives messages from the server (text), one of the main business logic entry points.
onClose(int code, String reason, boolean remote)	Callback when the connection is closed, can be used for resource cleanup or automatic reconnection.
onError(Exception ex)	Triggered when a network or protocol error occurs.
connect()	Initiates a connection operation (asynchronously), will automatically trigger onOpen and other events.
send(String message)	Sends a message to the server. Also supports send(ByteBuffer) to send binary data.

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