// 請(qǐng)求行（方法 + URL + 協(xié)議版本）
GET /api/user/1 HTTP/1.1
// 請(qǐng)求頭（鍵值對(duì)，描述請(qǐng)求信息）
Host: localhost:8080
User-Agent: Java/1.8.0_301
Accept: */*
// 空行（請(qǐng)求頭與請(qǐng)求體的分隔）
// 請(qǐng)求體（可選，POST/PUT請(qǐng)求攜帶參數(shù)，如JSON、表單）
{"name":"zhangsan","age":20}

// 響應(yīng)行（協(xié)議版本 + 狀態(tài)碼 + 狀態(tài)描述）
HTTP/1.1 200 OK
// 響應(yīng)頭（鍵值對(duì)，描述響應(yīng)信息）
Content-Type: application/json;charset=UTF-8
Content-Length: 50
// 空行
// 響應(yīng)體（接口返回的數(shù)據(jù)，如JSON）
{"code":200,"msg":"success","data":{"id":1,"name":"zhangsan"}}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpUrlConnectionDemo {
    public static void main(String[] args) throws Exception {
        // 1. 創(chuàng)建URL對(duì)象
        URL url = new URL("http://localhost:8080/api/user/1");
        // 2. 打開連接
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        // 3. 設(shè)置請(qǐng)求方法（GET/POST）
        conn.setRequestMethod("GET");
        // 4. 設(shè)置請(qǐng)求頭
        conn.setRequestProperty("Content-Type", "application/json");
        // 5. 發(fā)起請(qǐng)求，獲取響應(yīng)碼
        int responseCode = conn.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            // 6. 讀取響應(yīng)體
            BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            StringBuilder response = new StringBuilder();
            while ((line = br.readLine()) != null) {
                response.append(line);
            }
            br.close();
            System.out.println("響應(yīng)結(jié)果：" + response.toString());
        }
        // 7. 關(guān)閉連接
        conn.disconnect();
    }
}

<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>4.11.0</version>
</dependency>

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class OkHttpDemo {
    private static final OkHttpClient client = new OkHttpClient();

    public static void main(String[] args) throws Exception {
        // 1. 構(gòu)建請(qǐng)求
        Request request = new Request.Builder()
                .url("http://localhost:8080/api/user/1")
                .get()
                .addHeader("Content-Type", "application/json")
                .build();
        // 2. 發(fā)送請(qǐng)求，獲取響應(yīng)
        try (Response response = client.newCall(request).execute()) {
            if (response.isSuccessful()) {
                System.out.println("響應(yīng)結(jié)果：" + response.body().string());
            }
        }
    }
}

import org.springframework.web.client.RestTemplate;
public class RestTemplateDemo {
    public static void main(String[] args) {
        // 1. 創(chuàng)建RestTemplate實(shí)例
        RestTemplate restTemplate = new RestTemplate();
        // 2. 發(fā)送GET請(qǐng)求，獲取響應(yīng)（自動(dòng)解析JSON為對(duì)象）
        String url = "http://localhost:8080/api/user/1";
        String response = restTemplate.getForObject(url, String.class);
        System.out.println("響應(yīng)結(jié)果：" + response);
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class TcpServer {
    public static void main(String[] args) throws Exception {
        // 1. 創(chuàng)建ServerSocket，監(jiān)聽指定端口（10086）
        ServerSocket serverSocket = new ServerSocket(10086);
        System.out.println("TCP服務(wù)器已啟動(dòng)，等待客戶端連接...");

        // 2. 等待客戶端連接（阻塞式）
        Socket clientSocket = serverSocket.accept();
        System.out.println("客戶端已連接：" + clientSocket.getInetAddress());

        // 3. 讀取客戶端發(fā)送的數(shù)據(jù)
        BufferedReader br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        String clientMsg = br.readLine();
        System.out.println("收到客戶端消息：" + clientMsg);

        // 4. 向客戶端發(fā)送響應(yīng)
        OutputStreamWriter osw = new OutputStreamWriter(clientSocket.getOutputStream());
        osw.write("服務(wù)器已收到消息：" + clientMsg + "\n");
        osw.flush();

        // 5. 關(guān)閉資源
        osw.close();
        br.close();
        clientSocket.close();
        serverSocket.close();
    }
}

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;

public class TcpClient {
    public static void main(String[] args) throws Exception {
        // 1. 連接服務(wù)器（IP+端口）
        Socket socket = new Socket("localhost", 10086);

        // 2. 向服務(wù)器發(fā)送數(shù)據(jù)
        OutputStreamWriter osw = new OutputStreamWriter(socket.getOutputStream());
        osw.write("Hello TCP Server!\n");
        osw.flush();

        // 3. 讀取服務(wù)器響應(yīng)
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String serverMsg = br.readLine();
        System.out.println("收到服務(wù)器消息：" + serverMsg);

        // 4. 關(guān)閉資源
        br.close();
        osw.close();
        socket.close();
    }
}

import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UdpServer {
    public static void main(String[] args) throws Exception {
        // 1. 創(chuàng)建DatagramSocket，監(jiān)聽指定端口（10087）
        DatagramSocket socket = new DatagramSocket(10087);
        System.out.println("UDP服務(wù)器已啟動(dòng)，等待客戶端消息...");

        // 2. 接收客戶端數(shù)據(jù)（創(chuàng)建數(shù)據(jù)報(bào)，用于存儲(chǔ)接收的數(shù)據(jù)）
        byte[] buffer = new byte[1024];
        DatagramPacket receivePacket = new DatagramPacket(buffer, buffer.length);
        socket.receive(receivePacket); // 阻塞式接收

        // 3. 解析客戶端消息
        String clientMsg = new String(receivePacket.getData(), 0, receivePacket.getLength());
        System.out.println("收到客戶端消息：" + clientMsg);

        // 4. 向客戶端發(fā)送響應(yīng)
        String response = "服務(wù)器已收到消息：" + clientMsg;
        byte[] responseBytes = response.getBytes();
        // 獲取客戶端的IP和端口，用于回送響應(yīng)
        DatagramPacket sendPacket = new DatagramPacket(
                responseBytes, responseBytes.length,
                receivePacket.getAddress(), receivePacket.getPort()
        );
        socket.send(sendPacket);

        // 5. 關(guān)閉資源
        socket.close();
    }
}

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UdpClient {
    public static void main(String[] args) throws Exception {
        // 1. 創(chuàng)建DatagramSocket（無(wú)需指定端口，系統(tǒng)自動(dòng)分配）
        DatagramSocket socket = new DatagramSocket();

        // 2. 準(zhǔn)備發(fā)送的數(shù)據(jù)
        String msg = "Hello UDP Server!";
        byte[] msgBytes = msg.getBytes();
        // 3. 創(chuàng)建數(shù)據(jù)報(bào)（指定服務(wù)器IP、端口）
        DatagramPacket sendPacket = new DatagramPacket(
                msgBytes, msgBytes.length,
                InetAddress.getLocalHost(), 10087
        );
        // 4. 發(fā)送數(shù)據(jù)
        socket.send(sendPacket);

        // 5. 接收服務(wù)器響應(yīng)
        byte[] buffer = new byte[1024];
        DatagramPacket receivePacket = new DatagramPacket(buffer, buffer.length);
        socket.receive(receivePacket);
        String serverMsg = new String(receivePacket.getData(), 0, receivePacket.getLength());
        System.out.println("收到服務(wù)器消息：" + serverMsg);

        // 6. 關(guān)閉資源
        socket.close();
    }
}

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients // 開啟Feign RPC調(diào)用
public class ClientApplication {
    public static void main(String[] args) {
        SpringApplication.run(ClientApplication.class, args);
    }
}

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

// name：遠(yuǎn)程服務(wù)名稱（注冊(cè)中心中的服務(wù)名）
@FeignClient(name = "user-service")
public interface UserFeignClient {
    // 遠(yuǎn)程服務(wù)的接口路徑和請(qǐng)求方式
    @GetMapping("/api/user/{id}")
    String getUserById(@PathVariable("id") Integer id);
}}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ClientController {
    @Autowired
    private UserFeignClient userFeignClient;

    @GetMapping("/user/{id}")
    public String getUser(@PathVariable("id") Integer id) {
        // 調(diào)用遠(yuǎn)程服務(wù)方法
        return userFeignClient.getUserById(id);
    }
}