Java NIO blocking communication

package com.nio.t;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;


/*
 * 1. Use NIO to complete the three cores of network communication:
 *
 * 1. Channel: responsible for connection
 *         
 * java.nio.channels.Channel interface:
 *             |--SelectableChannel
 *                 |--SocketChannel
 *                 |--ServerSocketChannel   //TCP
 *                 |--DatagramChannel   //UDP
 *
 *                 |--Pipe.SinkChannel
 *                 |--Pipe.SourceChannel
 *
 * 2. Buffer: responsible for data access
 *
 * 3. Selector: It is a multiplexer of SelectableChannel. Used to monitor the IO status of SelectableChannel
 *
 */
public class TestBlockingNIO {

    // Client 
    public  void client() throws IOException{
         // 1. Get channel 
        SocketChannel sChannel = SocketChannel.open(
                         new InetSocketAddress( " 127.0.0.1 " , 9898 ));

        // At this time, all files are in FileChannel 
        FileChannel inChannel = FileChannel.open(Paths.get ( " D :\\1.txt " ),
                                    StandardOpenOption.READ);
        
        // 2. Allocate a buffer of the specified size 
        ByteBuffer buf = ByteBuffer.allocate( 1024 );
        
        // 3. Read the local file and send it to the server 
        while (inChannel.read(buf) != - 1 ){ // The file in FileChannel is read into the buffer 
            buf.flip();
            sChannel.write(buf); // Write the data in the buffer to the SocketChannel 
            buf.clear(); // Empty the buffer 
        }
         // After the loop, all files are sent to the SocketChannel
         // 4. Close channel 
        inChannel.close();
        sChannel.close();
    }
    
    // Server 
    public  void server() throws IOException{
         // 1. Get the channel, indicating that a ServerSocketChannel channel is opened on the machine 
        ServerSocketChannel ssChannel = ServerSocketChannel.open();

        // Indicates that an empty file is created locally, waiting for data to be written 
        FileChannel outChannel = FileChannel.open(Paths.get ( " D :\\2.txt " ),
                                    StandardOpenOption.WRITE,
                                    StandardOpenOption.CREATE);
        // 2. Bind the port 
        ssChannel.bind( new InetSocketAddress( 9898 ));
        
        // 3. Get the channel connected by the client, when the connection is established with the client, 
        SocketChannel sChannel = ssChannel.accept();
        
        // 4. Allocate a buffer of the specified size 
        ByteBuffer buf = ByteBuffer.allocate( 5 );
        
        // 5. Receive the client's data and save it to the local 
        while (sChannel.read(buf) != - 1 ){
             try {
                Thread.sleep(5000);
            }catch (Exception e){

            }
            buf.flip();
            outChannel.write(buf); // Write the data in the buffer to the file 
            buf.clear();
        }
        
        // 6. Close the channel 
        sChannel.close();
        outChannel.close();
        ssChannel.close();
        
    }

    public static void main(String[] args) {
        new Thread(()->{
            try {
                new TestBlockingNIO().client();
                System.out.println("client end....");
            }catch (Exception e){

            }

        }).start();
        new Thread(()->{
            try {
                new TestBlockingNIO().server();
                System.out.println("server end .....");
            }catch (Exception e){

            }
        }).start();
    }
    
}