阻塞式网络通信小案例：

package com.nio;

import com.sun.xml.internal.ws.server.ServerSchemaValidationTube;
import org.junit.Test;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
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;

/**
 * 一、使用NIO完成网络通信的三个核心
 * 1.通道（Channel）:负责连接
 *    java.nio.channels.Channel  接口
 *        |--SelectableChannel
 *           |--SocketChannel
 *           |--ServerSocketChannel
 *           |--DatagramChannel
 *
 *           |--Pipe.SinkChannel
 *           |--Pipe.SourceChannel
 *
 * 2.缓存区（Buffer）:负责数据的存取
 * 3.选择器（Selector）:是SelectableChannel 的多路复用器。用于监控SelectableChannel的IO状况
 *
 * 注意：在启动的时候，先启动服务端，再启动客户端
 */
public class TestBlockingNIO {
    //客户端
    @Test
    public void client() throws IOException {
        //1.获取通道
        SocketChannel sChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1", 9898));
        FileChannel inChannel = FileChannel.open(Paths.get("1.jpg"), StandardOpenOption.READ);
        //2.分配指定大小的缓存区
        ByteBuffer buf = ByteBuffer.allocate(1024);
        //3.读取本地文件，并发送到服务器端
        while (inChannel.read(buf)!=-1){
            buf.flip();
            sChannel.write(buf);
            buf.clear();
        }
        //4.关闭通道
        inChannel.close();
        sChannel.close();

    }
    //服务端
    @Test
    public void server() throws IOException {
     //1.获取通道
        ServerSocketChannel ssChannel = ServerSocketChannel.open();
        FileChannel outChannel = FileChannel.open(Paths.get("2.jpg"), StandardOpenOption.WRITE, StandardOpenOption.CREATE);//如果存在的话，就进行覆盖
        //2.绑定连接
        ssChannel.bind(new InetSocketAddress(9898));
        //3.获取客户端连接的通道
        SocketChannel sChannel = ssChannel.accept();
        //4.分配指定大小的缓存区
        ByteBuffer buf = ByteBuffer.allocate(1024);
        //5.接收客户端的数据，并保存到本地
        while (sChannel.read(buf)!=-1){
            buf.flip();
            outChannel.write(buf);
            buf.clear();
        }
        //6.关闭通道
        sChannel.close();
        outChannel.close();
        ssChannel.close();

    }
}