# NIO 實例demo-Client

NIO 實例demo-Client

Client部分包括Client和ClientHandle兩部分其中Client的時序通信圖如下

Client.java

Client端啓動主函數如下

package MyTestNetty.Server;
/**
 * Created by User on 2017/8/4.
 */
public class Client {
    public static void main(String[] args) {
        int port = 8080;//指定端口號
        new Thread(new TimeClientHandle1("127.0.0.1",port),"myclient").start();//啓動監聽線程
    }
}

TimeClientHandle1.java

第二部分是ClientHandler部分代碼如下：

package MyTestNetty.Server;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

/**
 * Created by User on 2017/8/4.
 */
public class TimeClientHandle1 implements Runnable {
    private String host;
    private int port;
    private Selector selector;
    private SocketChannel socketChannel;
    private volatile boolean stop;


    public TimeClientHandle1(String host, int port) {
        this.host = host == null ? "127.0.0.1" : host;
        this.port = port;

        try {
            selector = Selector.open();//創建selector實例
            socketChannel = SocketChannel.open();//創建socketChannel實例
            socketChannel.configureBlocking(false);//設置爲異步

        } catch (IOException e) {
            e.printStackTrace();
            System.exit(1);
        }
    }


    @Override
    public void run() {
        try{
            doConnect();
        }catch (IOException e){
            e.printStackTrace();
            System.exit(1);
        }

        while (!stop){//輪詢查詢可用的key
            try{
                selector.select(1000);
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> it = selectionKeys.iterator();
                SelectionKey key = null;
                while (it.hasNext()){
                    key = it.next();
                    it.remove();
                    try {
                        hadleInput(key);
                    }
                    catch (Exception e){
                        if(key!=null){
                            key.cancel();
                            if(key.channel()!=null)
                                key.channel().close();
                        }
                    }
                }
            }catch (Exception e){
                e.printStackTrace();
                System.exit(1);
            }
        }

        // 多路複用器關閉後，所有註冊在上面的Channel和Pipe等資源都會被自動註冊並關閉，所以不需要重新釋放資源
        if(selector!=null){
            try {
                selector.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }

    }

    private void hadleInput(SelectionKey key) throws IOException {
        if(key.isValid()){
            SocketChannel sc = (SocketChannel)key.channel();
            if(key.isConnectable()){
                if(sc.finishConnect()){
                    sc.register(selector,SelectionKey.OP_READ);
                    doWrite(sc);//向服務啓發送請求（先寫緩衝）
                }else{
                    System.exit(1);
                }

            }
            if(key.isReadable()){//讀取服務端返回的數據，從還緩衝中讀數據
                // read data
                ByteBuffer readBuffer = ByteBuffer.allocate(1024);
                int readBytes = sc.read(readBuffer);
                if(readBytes>0){
                    readBuffer.flip();
                    byte[] bytes=new byte[readBuffer.remaining()];
                    readBuffer.get(bytes);
                    String body = new String(bytes,"UTF-8");
                    System.out.println("Hello glad to see you : " + body);

                    this.stop=true;
                }
                else if(readBytes<0){
                    // 對端鏈路關閉
                    key.cancel();
                    sc.close();
                }
                else ; // 讀到0字節，忽略
            }
        }
    }



    private void doConnect() throws IOException {
        if(socketChannel.connect(new InetSocketAddress(host,port))){
            socketChannel.register(selector,SelectionKey.OP_READ);
            doWrite(socketChannel);
        }else{
            socketChannel.register(selector,SelectionKey.OP_CONNECT);
        }
    }
    private void doWrite(SocketChannel sc) throws IOException {
        byte[] req = "Clients ".getBytes();
        ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);
        writeBuffer.put(req);
        writeBuffer.flip();
        sc.write(writeBuffer);
        if(!writeBuffer.hasRemaining()){
            System.out.println("send order to server succeed!");
        }
    }
}

這一部分主要是包括向服務器發送請求，以及接受來自server的信息，啓動運行後可輸出一下結果表示服務端啓動成功（本例中我們向服務器發送的是Clients 字符串）服務器給我們反饋的是Server）

並且在服務端的控制檯輸出如下：

這個簡單的服務器客戶端NIO通信的簡單demo