java网络编程复习

计算机网络中的课程，我们运用java的网络编程，主要是在传输层应用（TCP/UDP）编程。
IP地址：java中提供InetAddress包，
java的网络编程也称为套接字编程。
以下是一个TCP例子，一个UDP例子

聊天案例：
服务端：

package com.cihiyuanzhang.tcp;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

//服务端
public class TcpServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket=null;
        Socket socket=null;
        InputStream inputStream=null;
        ByteArrayOutputStream baos=null;
        try {
            //1服务端有一个地址
            serverSocket=new ServerSocket(9999);
            //2等待客户端连接过来
            socket=serverSocket.accept();
            //3读取客户端信息
            inputStream=socket.getInputStream();
            //管道流
            baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024];
            int len;
            while ((len=inputStream.read(buffer))!=-1){
                baos.write(buffer,0,len);
            }
            System.out.println(baos.toString());


        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            //关闭资源
            baos.close();
            inputStream.close();
            socket.close();
            serverSocket.close();
        }

    }
}

客户端

package com.cihiyuanzhang.tcp;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

//客户端
public class TcpClient {
    public static void main(String[] args) throws IOException {
        InetAddress serverIP=null;
        Socket socket=null;
        OutputStream os=null;
        try {
            //要知道服务器地址，端口号
            serverIP = InetAddress.getByName("127.0.0.1");
            int port = 9999;
            //创建一个socket连接
            socket = new Socket(serverIP,port);
            //发送消息 IO流
            os = socket.getOutputStream();
            os.write("你好，欢迎学习".getBytes());
            
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            os.close();
            socket.close();
        }

    }
}

UDP发送消息例子
客户端1：

package com.cihiyuanzhang.udp;

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

public class UdpClientDemo1 {
    public static void main(String[] args) throws IOException {
        //1建立一个socket
        DatagramSocket socket = new DatagramSocket();
        //2建个包
        String msg ="你好啊，服务器";
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;
        //数据，数据的长度起始，要发给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);

        //3发送包
        socket.send(packet);
        //4关闭流
        socket.close();
    }
}

client2示例：

package com.cihiyuanzhang.udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

//服务端还是处于等待客户端的连接，处于监听状态
public class UdpServerDemo1 {
    public static void main(String[] args) throws IOException {
        //服务端开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet=new DatagramPacket(buffer,0,buffer.length); //接收
        
        socket.receive(packet);
        //关闭连接
        socket.close();

    }
}