网络_3_2010_03_14

UDP
不可靠
效率高
数据报
把一个字符串解析成为字节数组
new String(“hello”).getBytes();
UDP是无线的得写明IP和端口号

Long类型的数转换成字节数组

第十章总结
网络协议分层思想
IP的概念
TCP/UDP的概念
TCP/UDP程序的写法

代码清单：

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import java.net.*;
import java.io.*;

public class TestUDPServer{
public static void main(String [] args) throws Exception{

byte buf[] = new byte[1024];
DatagramPacket dp = new DatagramPacket(buf,buf.length);
DatagramSocket ds = new DatagramSocket(5678);
while(true){
ds.receive(dp);
ByteArrayInputStream bais = new ByteArrayInputStream(buf);
DataInputStream dis = new DataInputStream(bais);
System.out.println(dis.readLong());
}
}
}

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import java.net.*;
import java.io.*;

public class TestUDPClient{
public static void main(String [] args) throws Exception{

long n = 10000L;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
dos.writeLong(n);

byte[] buf = baos.toByteArray();//(new String("hello")).getBytes();
System.out.println(buf.length);
DatagramPacket dp = new DatagramPacket(buf,buf.length,
new InetSocketAddress("127.0.0.1",5678));
DatagramSocket ds = new DatagramSocket(9999);
ds.send(dp);
ds.close();
}
}