bio 实现

public class SocketServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(9000);
        while (true) {
            System.out.println("等待连接。。");
            //阻塞方法
            Socket socket = serverSocket.accept();
            System.out.println("有客户端连接了。。");
            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        handler(socket);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }).start();
            //handler(socket);

        }
    }

    private static void handler(Socket socket) throws IOException {
        System.out.println("thread id = " + Thread.currentThread().getId());
        byte[] bytes = new byte[1024];

        System.out.println("准备read。。");
        //接收客户端的数据，阻塞方法，没有数据可读时就阻塞
        int read = socket.getInputStream().read(bytes);
        System.out.println("read完毕。。");
        if (read != -1) {
            System.out.println("接收到客户端的数据：" + new String(bytes, 0, read));
            System.out.println("thread id = " + Thread.currentThread().getId());

        }
        socket.getOutputStream().write("HelloClient".getBytes());
        socket.getOutputStream().flush();
    }
}

client Srever:

public class SocketClient {

    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("127.0.0.1", 9000);
        //向服务端发送数据
        socket.getOutputStream().write("HelloServer".getBytes());
        socket.getOutputStream().flush();
        System.out.println("向服务端发送数据结束");
        byte[] bytes = new byte[1024];
        //接收服务端回传的数据
        socket.getInputStream().read(bytes);
        System.out.println("接收到服务端的数据：" + new String(bytes));
        socket.close();
    }
}