UDP知识点与案例：

DatagramPacket dp = new DatagramPacket(buf, buf.length); 后面的字节数组用于接收发进来的数据报。

DatagramPacket dp = new DatagramPacket(buf, buf.length,new InetSocketAddress("127.0.0.1", 5678));后面的inetsocketaddress是用户发送数据报的目标地址和端口号，以及发送的字节数组长度与字节数组。

DatagramSocket ds = new DatagramSocket(5678);//创建一个数据报套接字并绑定到本地具体的端口上。

Constructs a datagram socket and binds it to the specified port on the local host machine. The socket will be bound to the wildcardaddress, an IP address chosen by the kernel.

1 import java.net.*; 2 import java.io.*; 3  4 public class TestUDPClient 5 { 6     public static void main(String args[]) throws Exception 7     { 8         long n = 100000L; 9         ByteArrayOutputStream baos = new ByteArrayOutputStream();10         DataOutputStream dos = new DataOutputStream(baos);11         dos.writeLong(n);12         13         byte[] buf = baos.toByteArray();//转换为字节数组14 System.out.println(buf.length);15         DatagramPacket dp = new DatagramPacket(buf, buf.length,new InetSocketAddress("127.0.0.1", 5678));16         DatagramSocket ds = new DatagramSocket(9999);17         ds.send(dp);18         ds.close();19         20     }21 }

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());		}	}}

　　TCP知识点与典型案例：

1.客户端要创建Socket并且指定自己的ip地址和要绑定的端口号：Socket s1 = new Socket("127.0.0.1", 8888);

2.服务端要穿件serversocket并且连接到哪个端口号：ServerSocket s = new ServerSocket(8888);

3.服务器端的ServerSocket中的accept()方法用于接收客户端的连接请求，返回值为一个socket，常常用socket的getinputstream或getoutputstream方法获取流来进行交流。

1 *    要  点： 2  *        1. Java Socket编程步骤 3  *        2. Socket/ServerSocket类用法 4  *        3. 通过Socket对象可以获取通信对方Socket的信息 5  */ 6 import java.net.*; 7 import java.io.*; 8  9 public class TestServer {10     public static void main(String args[]) {11         try {        12             ServerSocket s = new ServerSocket(8888);13             while (true) {14                 Socket s1 = s.accept();15                 OutputStream os = s1.getOutputStream();16                 DataOutputStream dos = new DataOutputStream(os);17                 dos.writeUTF("Hello," + s1.getInetAddress() + 18                         "port#" +s1.getPort() + "  bye-bye!");19                 dos.close();20                 s1.close();21             }22         }catch (IOException e) {23             e.printStackTrace();24             System.out.println("程序运行出错:" + e);            25         }26     }27 }

1 /*    范例名称：简单的client/server程序 2  *     源文件名称：TestClient.java/TestServer.java 3  *    要  点： 4  *        1. Java Socket编程步骤 5  *        2. Socket/ServerSocket类用法 6  *        3. 通过Socket对象可以获取通信对方Socket的信息 7  */ 8  9 import java.net.*;10 import java.io.*;11 12 public class TestClient {13     public static void main(String args[]) {14         try {15             Socket s1 = new Socket("127.0.0.1", 8888);16             InputStream is = s1.getInputStream();17             DataInputStream dis = new DataInputStream(is);18             System.out.println(dis.readUTF());19             dis.close();20             s1.close();21         } catch (ConnectException connExc) {22             connExc.printStackTrace();23             System.err.println("服务器连接失败！");24         } catch (IOException e) {25             e.printStackTrace();26         }27     }28 }