网络通信小案例，服务端接收成功要给客户端一个反馈（阻塞式）

package com.nio;
import org.junit.Test;
import java.io.BufferedReader;
import java.io.File;
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.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
 
/**
 * 网络通信小案例
 */
public class TestBlockingNIO2 {
    public void client() throws Exception{
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
        FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        ByteBuffer buf = ByteBuffer.allocate(1024);
        while (inChannel.read(buf) != -1) {
            buf.flip();//切换成读模式
            sChannel.write(buf);
            buf.clear();
        }
        sChannel.shutdownOutput();
        //接收服务端的反馈
        int len=0;
        while ((len=sChannel.read(buf))!=-1){
            buf.flip();
            System.out.println(new String(buf.array(),0,len));
            buf.clear();
        }
        //关闭通道
        inChannel.close();
        sChannel.close();
 
    }
    @Test
    public void serve() throws Exception{
        ServerSocketChannel ssChannel = ServerSocketChannel.open();
        FileChannel outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);
        ssChannel.bind(new InetSocketAddress(9898));
        SocketChannel sChannel = ssChannel.accept();
        ByteBuffer buf = ByteBuffer.allocate(1024);
        while (sChannel.read(buf)!=-1){
            buf.flip();
            outChannel.write(buf);
            buf.clear();
        }
        //发送反馈给客户端
        buf.put("服务端接收数据成功".getBytes());
        buf.flip();
        sChannel.write(buf);
 
        //关闭通道
        sChannel.close();
        outChannel.close();
        ssChannel.close();
 
 
    }
 
 
}