最近在做 Socket开发，为了方便本地调试，特地写一个简单的 socket服务端，做回响（接收到什么回什么），并且用于客户端心跳测试。

EchoSocketServer .java

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 回响 Socket服务器
 */
public class EchoSocketServer {

    private static final int PORT = 8888;

    public static void main(String[] args) {
        EchoSocketServer server = new EchoSocketServer(PORT);
    }

    /**
     * 线程池
     */
    private ExecutorService executorService = null;
    /**
     * 服务
     */
    private ServerSocket serverSocket = null;
    /**
     * 客户端列表
     */
    private List<Socket> socketList = new ArrayList<>();

    private EchoSocketServer(int port) {

        try {
            // 创建服务器 socket
            serverSocket = new ServerSocket(port);
            // 初始化线程池
            executorService = Executors.newCachedThreadPool();
            System.out.println("服务启动完成，等待客户端连接...");

            Socket client = null;
            while (true) {
                client = serverSocket.accept();
                socketList.add(client);
                executorService.execute(new Service(client));
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

        // TODO
        // socketList 管理

    }

    private static class Service implements Runnable {

        /**
         * 20 秒超时服务器主动断开
         */
        private static final long TIMEOUT_MILLISECOND = 20000;

        private Socket socket;

        private boolean isConnect;
        private long lastReceiveTime = System.currentTimeMillis();

        public Service(Socket socket) {
            this.socket = socket;
            this.isConnect = true;
            System.out.println(socket.getInetAddress() + ":" + socket.getPort() + " <连接>");
        }

        @Override
        public void run() {

            while (isConnect) {
                // 超时
                if (System.currentTimeMillis() - lastReceiveTime > TIMEOUT_MILLISECOND) {
                    stopService();
                } else {
                    try {

                        // 默认接收 1024字节
                        byte[] bytes = new byte[1024];
                        InputStream in = socket.getInputStream();
                        if (in.available() > 0) {
                            lastReceiveTime = System.currentTimeMillis();
                            int len = in.read(bytes);

                            String content = new String(bytes);
                            System.out.println(socket.getInetAddress() + ":" + socket.getPort() + "  " + content);

                            // 回响
                            OutputStream os = socket.getOutputStream();
                            os.write(bytes);
                            os.flush();
                        } else {
                            Thread.sleep(10);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                        stopService();
                    }
                }

            }

        }

        /**
         * 断开客户端
         */
        private void stopService() {
            isConnect = false;
            System.out.println(socket.getInetAddress() + ":" + socket.getPort() + " <断开>");
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}