java分布式开发TCP/IP NIO无阻塞 Socket（(基于消息方式实现系统间的通信) ）

转自：https://www.iteye.com/blog/mars914-1238353

在java中可以基于java.nio.channels中的Channel和Selector的相关类来实现TCP/IP+NIO方式的系统间通信。

用于系统间通信依靠SocketChannel和ServerSocketChannel，SocketChannel用于建立连接，监听事件及操作读写，ServerSocketChannel用于监听端口及监听连接事件，可通过Selector来获取是否有要处理的事件。

服务端java代码：

package com.java.distributed.message.tcpip;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;

public class NIOServer {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        int port =7889;
        //打开选择器
        Selector selector=Selector.open();
        //打开服务器套接字通道
        ServerSocketChannel ssc=ServerSocketChannel.open();
        //检索与此通道关联的服务器套接字
        ServerSocket serverSocket=ssc.socket();
        //将 ServerSocket 绑定到特定地址（IP 地址和端口号）
        serverSocket.bind(new InetSocketAddress(port));
        System.out.println("server listen on port:"+port);

        //调整通道的阻塞模式
        ssc.configureBlocking(false);
        //向给定的选择器注册此通道，返回一个选择键。SelectionKey.OP_ACCEPT--用于套接字接受操作的操作集位
        ssc.register(selector, SelectionKey.OP_ACCEPT);

        while(true){
            //timeout:为正，则在等待某个通道准备就绪时最多阻塞 timeout 毫秒；如果为零，则无限期地阻塞；必须为非负数
            int nKeys=selector.select(1000);
            if(nKeys>0){

                for(SelectionKey key:selector.selectedKeys()){
                    /*测试此键的通道是否已准备好接受新的套接字连接--
                     * 如果此键的通道不支持套接字接受操作，则此方法始终返回 false
                     * */
                    if(key.isAcceptable()){
                        ServerSocketChannel server=(ServerSocketChannel) key.channel();
                        SocketChannel sc=server.accept();

                        if(sc==null){
                            continue;
                        }
                        sc.configureBlocking(false);
                        sc.register(selector, SelectionKey.OP_READ);
                    }else if(key.isReadable()){
                        //分配一个新的字节缓冲区
                        ByteBuffer buffer=ByteBuffer.allocate(1024);
                        SocketChannel sc=(SocketChannel) key.channel();
                        int readBytes=0;
                        String message=null;
                        try{
                            int ret;
                            try{
                                while((ret=sc.read(buffer))>0){
                                    readBytes +=ret;
                                }

                            }catch(Exception e ){
                                readBytes=0;
                                //ignore
                            }finally{
                                //反转此缓冲区。首先对当前位置设置限制，然后将该位置设置为零
                                buffer.flip();
                            }

                            if(readBytes>0){
                                message=Charset.forName("UTF-8").decode(buffer).toString();
                                buffer=null;
                            }
                        }finally{
                            if(buffer!=null)
                                buffer.clear();
                        }

                        if(readBytes>0){
                            System.out.println("message from client:"+message);
                            if("quit".equalsIgnoreCase(message.trim())){
                                sc.close();
                                selector.close();
                                System.out.println("Server has been shutdown!");
                                System.exit(0);
                            }
                            String outMessage="server response:"+message;
                            sc.write(Charset.forName("UTF-8").encode(outMessage));
                        }

                    }
                }
                selector.selectedKeys().clear();
            }

        }
    }
}

客户端java代码：

package com.java.distributed.message.tcpip;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;


public class NIOClient {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        int port =7889;
        SocketChannel channel=SocketChannel.open();
        channel.configureBlocking(false);

        SocketAddress target=new InetSocketAddress("127.0.0.1",port);
        channel.connect(target);
        Selector selector=Selector.open();
        //用于套接字连接操作的操作集位
        channel.register(selector, SelectionKey.OP_CONNECT);
        BufferedReader systemIn=new BufferedReader(new InputStreamReader(System.in));

        while(true){
            if(channel.isConnected()){
                String command=systemIn.readLine();
                channel.write(Charset.forName("UTF-8").encode(command));

                if(command==null||"quit".equalsIgnoreCase(command.trim())){
                    systemIn.close();
                    channel.close();
                    selector.close();
                    System.out.println("Client quit !");
                    System.exit(0);
                }
            }
            int nKeys=selector.select(1000);
            if(nKeys>0){
                for(SelectionKey key:selector.selectedKeys()){
                    if(key.isConnectable()){
                        SocketChannel sc=(SocketChannel) key.channel();
                        sc.configureBlocking(false);
                        sc.register(selector, SelectionKey.OP_READ);
                        sc.finishConnect();
                    }else if(key.isReadable()){
                        ByteBuffer buffer=ByteBuffer.allocate(1024);
                        SocketChannel sc=(SocketChannel) key.channel();
                        int readBytes=0;
                        try{
                            int ret=0;
                            try{
                                while((ret=sc.read(buffer))>0){
                                    readBytes+=ret;
                                }
                            }finally{
                                buffer.flip();
                            }
                            if (readBytes > 0) {
                                System.out.println(Charset.forName("UTF-8")
                                        .decode(buffer).toString());
                                buffer = null;
                            }

                        }finally {
                            if (buffer != null) {
                                buffer.clear();
                            }
                        }
                    }
                }
                    selector.selectedKeys().clear();
            }
        }
    }

}