Java 與 C# Socket 通訊：TCP 文本收發核心代碼範例 (含編碼、換行、緩衝處理)

協議約定

• 編碼：UTF-8
• 訊息分隔：\n (單行文本)
• 連線保持：長連接，雙向收發

Java 伺服端 (Server)

public class JavaServer {
    public static void main(String[] args) throws IOException {
        try (ServerSocket server = new ServerSocket(8888)) {
            System.out.println("Java Server listening on 8888...");
            while (true) {
                Socket client = server.accept();
                new Thread(() -> handle(client)).start();
            }
        }
    }

    static void handle(Socket socket) {
        try (BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream(), StandardCharsets.UTF_8));
             PrintWriter out = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), StandardCharsets.UTF_8), true)) {

            String line;
            while ((line = in.readLine()) != null) { // 讀取以 \n 結尾的行
                System.out.println("Recv from C#: " + line);
                // 回覆
                out.println("Java Echo: " + line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

C# 客戶端

using System;
using System.Net.Sockets;
using System.Text;
using System.Threading;

public class CSharpClient {
    public static void Main() {
        using (TcpClient client = new TcpClient("127.0.0.1", 8888))
        using (NetworkStream stream = client.GetStream())
        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
        using (StreamWriter writer = new StreamWriter(stream, Encoding.UTF8) { AutoFlush = true }) {

            // 發送
            writer.WriteLine("Hello from C#");
            // 接收
            string reply = reader.ReadLine();
            Console.WriteLine("Recv from Java: " + reply);

            // 持續互動
            while (true) {
                Console.Write("> ");
                string input = Console.ReadLine();
                if (input == "exit") break;
                writer.WriteLine(input);
                Console.WriteLine("Server: " + reader.ReadLine());
            }
        }
    }
}

關鍵細節

擴展：二進制/長訊息協議

若需傳輸 JSON/Protobuf 等二進制資料，改用「長度前綴 (4 bytes) + Payload」協議，雙端用 DataInputStream/BinaryReader 讀寫。