Socket编程

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.

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

public class TestUDPClient
{
    public static void main(String args[]) throws Exception
    {
        long n = 100000L;
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        dos.writeLong(n);
        
        byte[] buf = baos.toByteArray();//转换为字节数组
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();
        
    }
}

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。

*    要  点：
 *        1. Java Socket编程步骤
 *        2. Socket/ServerSocket类用法
 *        3. 通过Socket对象可以获取通信对方Socket的信息
 */
import java.net.*;
import java.io.*;

public class TestServer {
    public static void main(String args[]) {
        try {        
            ServerSocket s = new ServerSocket(8888);
            while (true) {
                Socket s1 = s.accept();
                OutputStream os = s1.getOutputStream();
                DataOutputStream dos = new DataOutputStream(os);
                dos.writeUTF("Hello," + s1.getInetAddress() + 
                        "port#" +s1.getPort() + "  bye-bye!");
                dos.close();
                s1.close();
            }
        }catch (IOException e) {
            e.printStackTrace();
            System.out.println("程序运行出错:" + e);            
        }
    }
}

/*    范例名称：简单的client/server程序
 *     源文件名称：TestClient.java/TestServer.java
 *    要  点：
 *        1. Java Socket编程步骤
 *        2. Socket/ServerSocket类用法
 *        3. 通过Socket对象可以获取通信对方Socket的信息
 */

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

public class TestClient {
    public static void main(String args[]) {
        try {
            Socket s1 = new Socket("127.0.0.1", 8888);
            InputStream is = s1.getInputStream();
            DataInputStream dis = new DataInputStream(is);
            System.out.println(dis.readUTF());
            dis.close();
            s1.close();
        } catch (ConnectException connExc) {
            connExc.printStackTrace();
            System.err.println("服务器连接失败！");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}