package nioDemo;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.DatagramChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.charset.Charset;
import java.util.Iterator;
public class ClientDatagramChannelDemo {
public static class UDPEchoClient implements Runnable{
private String name;
private InetSocketAddress serviceAddress;
public UDPEchoClient(String name, InetSocketAddress serviceAddress){
this.name = name;
this.serviceAddress = serviceAddress;
}
@Override
public void run(){
DatagramChannel dc = null;
try{
/*每个实际上可以创建多个通道连接同一个服务器地址，
我们这里为了演示方便，只创建了一个通道*/
dc = DatagramChannel.open();
/*客户端采用非阻塞模式*/
dc.configureBlocking(false);
/*这里的连接不是指TCP的握手连接，因为UDP协议本身不需要连接，
*这里连接的意思大概是提前向操作系统申请好本地端口号，以及高速操作系统要发送的目的
*连接后的UDP通道可以提高发送的效率，还可以调用read和write方法接收和发送数据
*未连接的UDP通道只能调用receive和send方法接收和发送数据*/
dc.connect(serviceAddress);
Selector selector = Selector.open();
int interest = SelectionKey.OP_READ | SelectionKey.OP_WRITE;
dc.register(selector, interest, new Buffers(256, 256));
int i = 0;
while(!Thread.currentThread().isInterrupted()){
selector.select();
Iterator<SelectionKey> it = selector.selectedKeys().iterator();
while(it.hasNext()){
SelectionKey key = it.next();
it.remove();
Buffers buffers = (Buffers)key.attachment();
ByteBuffer readBuffer = buffers.getReadBuffer();
ByteBuffer writeBuffer = buffers.gerWriteBuffer();
try{
if(key.isReadable()){
dc.read(readBuffer);
readBuffer.flip();
CharBuffer charBuffer = Charset.defaultCharset().decode(readBuffer);
System.out.println(charBuffer.array());
readBuffer.clear();
}
if(key.isWritable()){
writeBuffer.put((name + (i++)).getBytes());
writeBuffer.flip();
dc.write(writeBuffer);
writeBuffer.clear();
Thread.sleep(500);
}
}catch(IOException e){
key.cancel();
key.channel().close();
}
}
}
}catch(InterruptedException e){
System.out.println(name + "interrupted");
} catch (IOException e) {
System.out.println(name + "encounter connect error");
} finally{
try {
dc.close();
} catch (IOException e) {
System.out.println(name + "encounter close error");
}finally{
System.out.println(name + "closed");
}
}
}
}
public static void main(String[] args){
InetSocketAddress serviceAddress = new InetSocketAddress("192.168.1.100", 8080);
UDPEchoClient clientA = new UDPEchoClient("thread a ", serviceAddress);
UDPEchoClient clientB = new UDPEchoClient("thread b ", serviceAddress);
UDPEchoClient clientC = new UDPEchoClient("thread c ", serviceAddress);
new Thread(clientA).start();
new Thread(clientB).start();
new Thread(clientC).start();
}
}