socket

网络编程

如何定位到网络上的一台主机

tcp

• 稳定

• 三次握手
  最少需要三次

• 四次挥手
  二次确认

UDP

• 不连接不稳定
• 不考虑接收者的情况
• DDOS

TCP实现聊天

package com.example.demo.utils;
       import org.apache.catalina.connector.OutputBuffer;
       import java.io.*;
       import java.net.InetAddress;
       import java.net.ServerSocket;
       import java.net.Socket;
//接收
public class ScoketDemo {
   public static void main(String[] args) {
       ServerSocket serverSocket = null;
       Socket socket = null;
       BufferedReader read = null;
       try {
           //创建socket服务
           int port = 9999;
           serverSocket = new ServerSocket(port);
           while(true) {
               //接受连接,形成传输通道
               socket = serverSocket.accept();
               //从socket写到内存中，对于内存是输入所以是输入流
               read = new BufferedReader(new InputStreamReader(socket.getInputStream()));
               System.out.println(read.readLine());
           }
       } catch (IOException e) {
           e.printStackTrace();
       } finally {
           if(read != null) {
               try {
                   read.close();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
           if(socket != null) {
               try {
                   socket.close();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
           if(serverSocket != null) {
               try {
                   serverSocket.close();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
       }
   }
}
//发送
class client{
   public static void main(String[] args) {
       Socket socket = null;
       PrintWriter writer = null;
       try {
           //连接到socket服务器
           socket = new Socket("127.0.0.1", 9999);
           //写数据到socket
           writer = new PrintWriter(socket.getOutputStream(), true);
       } catch (IOException e) {
           e.printStackTrace();
       } finally {
           if (writer != null) {
               writer.close();
           }
           if (socket != null) {
               try {
                   socket.close();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
       }
   }
}

UDP实现消息发送

class UdpClient {
    public static void main(String[] args) throws IOException {
        //创建socket
        DatagramSocket socket = new DatagramSocket();
        //创建数据包
        DatagramPacket packet = new DatagramPacket("msg".getBytes(), 0, "msg".getBytes().length, InetAddress.getByName("localhost"), 9999);
        //发送数据包
        socket.send(packet);
    }
}
class UdpServer {
    public static void main(String[] args) throws IOException {
        //开放端口
        DatagramSocket server = new DatagramSocket(9999);
        //定义数据包
        DatagramPacket datagramPacket = new DatagramPacket(new byte[1024],0,new byte[1024].length);
        //阻塞接受
        server.receive(datagramPacket);
        System.out.println(datagramPacket.getAddress().getHostAddress());
        System.out.println(datagramPacket.getData());
    }
}

使用udp实现连天功能

发送者

import java.io.IOException;
import java.net.*;
import java.util.Scanner;
public class UdpSender {
    public static void main(String[] args) throws IOException {
        DatagramSocket socket = new DatagramSocket(9998);
        while(true) {
            Scanner sc  = new Scanner(System.in);
            String msg = sc.nextLine();
            InetAddress inetAddress = InetAddress.getByName("localhost");
            DatagramPacket datagramPacket = new DatagramPacket(msg.getBytes(), 0, msg.length(), inetAddress, 9999);
            socket.send(datagramPacket);
        }
    }
}