java nio client sample

 

This code is reference from Mrs sun, a good female author.

notice: 1 nio including Buffer Channel Selector and optional Charset. actually there are two Buffers, one for accept ing message and one for sending.

2 return /r/n for line end

3 attendtion to buffer issue

4 attendtion to select key issue

I change little bit: 1 add handshaking process  2 add heartbeat process

package socket.nio;

import java.net.*;
import java.nio.channels.*;
import java.nio.*;
import java.io.*;
import java.nio.charset.*;
import java.util.*;

public class EchoClient ...{
    private SocketChannel socketChannel = null;
    private ByteBuffer sendBuffer = ByteBuffer.allocate(1024);
    private ByteBuffer receiveBuffer = ByteBuffer.allocate(1024);
    private Charset charset = Charset.forName("SJIS");
    private Selector selector;

    public EchoClient() throws IOException ...{
    socketChannel = SocketChannel.open();
    InetAddress ia = InetAddress.getLocalHost();
    InetSocketAddress isa = new InetSocketAddress(ia, 31000);
    socketChannel.connect(isa);
    socketChannel.configureBlocking(false);
    System.out.println("與服務器的連接建立成功");
    selector = Selector.open();
    }

    public static void main(String args[]) throws IOException ...{
    final EchoClient client = new EchoClient();
    Thread receiver = new Thread() ...{
        public void run() ...{
        client.keepConnection();
        }
    };
    client.sendBuffer.put(client.encode("C:Socket 18750 8 "));
    client.sendBuffer.put(client.encode("C:Start 0 "));

    receiver.start();
    client.talk();
    }

    public void keepConnection() ...{
    String msg = "C:HB";

    while (true) ...{
        try ...{
        Thread.sleep(1000);
        } catch (InterruptedException e) ...{
        e.printStackTrace();
        }
        synchronized (sendBuffer) ...{
        sendBuffer.put(encode(msg + " "));
        }
        System.out.println("time: "+System.currentTimeMillis() +" <== C:HB");
        if (msg.equals("bye"))
        break;
    }
    }

    public void talk() throws IOException ...{
    socketChannel.register(selector, SelectionKey.OP_READ
        | SelectionKey.OP_WRITE);
    while (selector.select() > 0) ...{
        Set readyKeys = selector.selectedKeys();
        Iterator it = readyKeys.iterator();
        while (it.hasNext()) ...{
        SelectionKey key = null;
        try ...{
            key = (SelectionKey) it.next();
            it.remove();

            if (key.isReadable()) ...{
            receive(key);
            }
            if (key.isWritable()) ...{
            send(key);
            }
        } catch (IOException e) ...{
            e.printStackTrace();
            try ...{
            if (key != null) ...{
                key.cancel();
                key.channel().close();
            }
            } catch (Exception ex) ...{
            e.printStackTrace();
            }
        }
        }//#while
        try ...{
        Thread.sleep(1);
        } catch (InterruptedException e) ...{
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
    }//#while
    }

    public void send(SelectionKey key) throws IOException ...{
    SocketChannel socketChannel = (SocketChannel) key.channel();
    synchronized (sendBuffer) ...{
        sendBuffer.flip(); //把極限設爲位置
        socketChannel.write(sendBuffer);
        sendBuffer.compact();
    }
    }

    public void receive(SelectionKey key) throws IOException ...{
    SocketChannel socketChannel = (SocketChannel) key.channel();
    socketChannel.read(receiveBuffer);
    receiveBuffer.flip();
    String receiveData = decode(receiveBuffer);

    if (receiveData.indexOf(" ") == -1)
        return;

    String outputData = receiveData.substring(0,
        receiveData.indexOf(" ") + 1);
    System.out.println("time:"+System.currentTimeMillis() + " ==> " + outputData);
    if (outputData.equals("C:End ")) ...{
        key.cancel();
        socketChannel.close();
        System.out.println("關閉與服務器的連接");
        selector.close();
        System.exit(0);
    }

    ByteBuffer temp = encode(outputData);
    receiveBuffer.position(temp.limit());
    receiveBuffer.compact();
    }

    public String decode(ByteBuffer buffer) ...{ //解碼
    CharBuffer charBuffer = charset.decode(buffer);
    return charBuffer.toString();
    }

    public ByteBuffer encode(String str) ...{ //編碼
    return charset.encode(str);
    }
}

/** *//****************************************************
 * 作者：孫衛琴                                     *
 * 來源：<<Java網絡編程精解>>                       *
 * 技術支持網址：www.javathinker.org                *
 ***************************************************/