服务端:
@Data
@Component
public class DelongServerSocket {
    @Value("${socket.port}")
    private Integer port;
    private boolean started;
    private ServerSocket ss;
    public static ConcurrentHashMap<String, ClientSocket> clientsMap = new ConcurrentHashMap<>();
    private ExecutorService executorService = Executors.newCachedThreadPool();

    public static void main(String[] args) {
        System.out.println("进入main:");
        new DelongServerSocket().start(10086);
    }

    public void start() {
        start(null);
    }

    public void start(Integer port) {
        try {
            ss = new ServerSocket(port == null ? this.port : port);
            started = true;
            System.out.println("端口已开启,占用端口号...."+this.port);
        } catch (Exception e) {
            System.out.println("端口使用中....");
            System.out.println("请关掉相关程序并重新运行服务器！");
            e.printStackTrace();
            System.exit(0);
        }
        int count = 0;
        try {
            while (started) {
                Socket socket = ss.accept();
                socket.setKeepAlive(true);
                count++;
                ClientSocket register = ClientSocket.register(socket,count);
                System.out.println("a client connected!");
                if (register != null) {
                    executorService.submit(register);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                ss.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

客户端线程:
@Data
@Slf4j
public class ClientSocket implements Runnable {

    private Socket socket;
    private DataInputStream inputStream;
    private DataOutputStream outputStream;
    private String key;
    private String message;

    /**
     * 注册socket到map里
     *
     * @param socket
     * @return
     */
    public static ClientSocket register(Socket socket,int count) throws Exception {
        ClientSocket client = new ClientSocket();
        try {
            client.setSocket(socket);
            client.setInputStream(new DataInputStream(socket.getInputStream()));
            client.setOutputStream(new DataOutputStream(socket.getOutputStream()));
            System.out.println("客户端的IP："+socket.getInetAddress().getHostAddress());
            System.out.println("user" + count+"正在登录...");
            client.setKey("user"+count);
            DelongServerSocket.clientsMap.put(client.getKey(), client);
            System.out.println(DelongServerSocket.clientsMap);
            return client;
        } catch (Exception e) {
            client.logout();
        }
        return null;
    }

    /**
     * 发送数据
     *
     * @param str
     */
    public void send(String str) throws Exception {
        System.out.println("服务端发送:======" + str);
        try {
            outputStream.write(str.getBytes());
        } catch (Exception e) {
            logout();
        }
    }

    /**
     * 接收数据
     *
     * @return
     * @throws Exception
     */
    public String receive() throws Exception {
        try {
            byte[] bytes = new byte[1024];
            inputStream.read(bytes);
            String info = new String(bytes, "utf-8");
            System.out.println("服务端接收：===" + info);
            return info;
        } catch (Exception e) {
            logout();
        }
        return null;
    }

    /**
     * 登出操作, 关闭各种流
     */
    public void logout() throws Exception {
        if (DelongServerSocket.clientsMap.containsKey(key)) {
            DelongServerSocket.clientsMap.remove(key);
        }

        System.out.println(DelongServerSocket.clientsMap);
        try {
//            socket.shutdownOutput();
//            socket.shutdownInput();
            inputStream.close();
            outputStream.close();
        } catch (Exception e) {
            throw new Exception("关闭输入输出异常", e);
        } finally {
            try {
                socket.close();
            } catch (Exception e) {
                throw new Exception("关闭socket异常", e);
            }
        }
    }

    /**
     * 发送数据包, 判断数据连接状态
     *
     * @return
     */
    public boolean isSocketClosed() {
        try {
            //socket.sendUrgentData(1);
            //发送
            Socket socket1 = DelongServerSocket.clientsMap.get("user1").getSocket();
            socket1.getOutputStream().write("测试1".getBytes(StandardCharsets.UTF_8));
            //socket.getOutputStream().write("测试".getBytes(StandardCharsets.UTF_8));
            //接收
            byte[] bytes = new byte[1024];
            socket.getInputStream().read(bytes);
            String receive = new String(bytes, "utf-8");
            System.out.println("服务端接收消息" + receive);
            return false;
        } catch (Exception e) {
            return true;
        }
    }

    @Override
    public void run() {
        // 每过5秒连接一次客户端
        while (true) {
            try {
                TimeUnit.SECONDS.sleep(5);
                if (isSocketClosed()) {
                    System.out.println("关闭");
                    logout();
                    break;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

        }

    }

    @Override
    public String toString() {
        return "Client{" +
                "socket=" + socket +
                ", inputStream=" + inputStream +
                ", outputStream=" + outputStream +
                ", key='" + key + '\'' +
                '}';
    }

}

客户端1:
public class ChatClient {
    public static void main(String[] args) throws Exception {
        String host = "127.0.0.1";
        int port = 8082;
        // 与服务端建立连接
        Socket socket = new Socket(host, port);
        socket.setOOBInline(true);
        // 建立连接后获得输出流
        DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
        DataInputStream inputStream = new DataInputStream(socket.getInputStream());
        int i=0;
        while (true) {
            send("客户端测试"+i,outputStream);
            receive(inputStream);
            i++;
        }
    }

    /**
     * 发送数据
     *
     * @param str
     */
    public static void send(String str,DataOutputStream outputStream) throws Exception {
        System.out.println("客户端发送:======"+str);
        try {
            outputStream.write(str.getBytes());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 接收数据
     *
     * @return
     * @throws Exception
     */
    public static String receive(DataInputStream inputStream) throws Exception {
        try {
            byte[] bytes = new byte[1024];
            inputStream.read(bytes);
            String info = new String(bytes, "utf-8");
            System.out.println("客户端接收：==="+info);
            return info;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}

客户端2:
public class ChatClient2 {
    public static void main(String[] args) throws Exception {
        String host = "127.0.0.1";
        int port = 8082;
        // 与服务端建立连接
        Socket socket = new Socket(host, port);
        socket.setOOBInline(true);
        // 建立连接后获得输出流
        DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
        DataInputStream inputStream = new DataInputStream(socket.getInputStream());
        int i=0;
        while (true) {
            send("客户端2测试"+i,outputStream);
            //receive(inputStream);
            i++;
        }
    }

    /**
     * 发送数据
     *
     * @param str
     */
    public static void send(String str,DataOutputStream outputStream) throws Exception {
        System.out.println("客户端发送:======"+str);
        try {
            outputStream.write(str.getBytes());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 接收数据
     *
     * @return
     * @throws Exception
     */
    public static String receive(DataInputStream inputStream) throws Exception {
        try {
            byte[] bytes = new byte[1024];
            inputStream.read(bytes);
            String info = new String(bytes, "utf-8");
            System.out.println("客户端接收：==="+info);
            return info;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}


服务端启动:

@SpringBootApplication
@Controller
public class DemoApplication {

    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(DemoApplication.class, args);
        context.getBean(DelongServerSocket.class).start();

    }

}