网络编程笔记

域名和端口号

网络通讯协议

TCP和UDP

编辑 InetAddress类

域名和端口号

注意：1.网络开发中不要使用0-1024的端口

2.端口号不能重复，否则会出现端口被占用的情况

网络通讯协议

人和人交流（通讯）：依靠语言【中文，英语，日语...】

语言本身就是一种协议。

在网络编程中，数据的组织形式就是协议。

TCP和UDP

InetAddress类

用法


//获取本机的InetAddress对象
        InetAddress localHost = InetAddress.getLocalHost();
        System.out.println(localHost);
        //2.根据指定的主机名获取 InetAddress对象
        InetAddress host1 = InetAddress.getByName("DESKTOP-6HLDCVM");
        System.out.println(host1);
 
        //3.根据域名 返回InetAddress对象比如 www.baidu.com
        InetAddress host2 = InetAddress.getByName("www.baidu.com");
        System.out.println(host2);
        //4.通过返回InetAddress对象 反向获取地址
        String hostAddress = host2.getCanonicalHostName();
        System.out.println(hostAddress);
        //5. 通过INetAddress 获取域名/主机名
        String hostName = host2.getHostName();
        String hostName2 = host1.getHostName();
        System.out.println(hostName);
        System.out.println(hostName2);

网络多线程_Socket （套接字）

发起连接的一方通过Socket调用OutputStream将数据写到数据通道中，然后接收方通过Socket调用InputStream读取数据。结束连接的时候要关闭Socket。

小练习

思路分析

客户端


public class Scoket02 {
    public static void main(String[] args) throws IOException {
        //1.连接本机的9999端口 ，连接成功返回一个socket对象
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        System.out.println("socket对象获取");
        //得到和 socket对象关联的输出流对象
        OutputStream outputStream = socket.getOutputStream();
        //通过输出流 写入数据到通道
        outputStream.write("hello".getBytes());
        //关闭流
        socket.close();
        outputStream.close();
        System.out.println("客户端关闭");
    }
}

服务端


//服务端
public class Socket01 {
    public static void main(String[] args) throws IOException {
        //在本机的9999端口监听，等待连接
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("服务端在9999监听");
        //当没有客户端连接9999端口时，程序会阻塞，等待连接
        Socket socket = serverSocket.accept();//当有客户端连接时会返回一个 socket对象
        System.out.println("有客户连接，正在获取数据");
        //通过socket 获取通道中的数据
        InputStream inputStream = socket.getInputStream();
        //IO读取
        byte[] buf =new byte[1024];
        int readLen = 0;
        while ((readLen = inputStream.read(buf)) != -1){
            System.out.println(new String(buf,0,readLen));
        }
        //关闭流
        inputStream.close();
        socket.close();
        serverSocket.close();
 
    }
}

小练习2


public class Socket03 {
    public static void main(String[] args) throws IOException {
        //服务器在9999端口监听
        ServerSocket serverSocket = new ServerSocket(9999);
        //等待客户端连接
        System.out.println("等待用户端连接");
        Socket socket = serverSocket.accept();
        //有客户端连接 读取通道内消息
        InputStream inputStream = socket.getInputStream();
        int readlen = 0;
        byte[] buf = new byte[1024];
        while ((readlen = inputStream.read(buf)) != -1 ){
            System.out.println(new String(buf,0,readlen));
        }
        //获取数据后准备，回信
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("hello,client".getBytes());
        socket.shutdownOutput();
        //关闭流
        outputStream.close();
        inputStream.close();
        socket.close();
        serverSocket.close();
        System.out.println("服务端退出");
    }
}


public class Socket04 {
    public static void main(String[] args) throws IOException {
        //连接到9999端口
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        //发送消息
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("hello server".getBytes());
        System.out.println("等待对方回信");
        socket.shutdownOutput();
        //接收回信
        InputStream inputStream = socket.getInputStream();
        int i = 0;
        byte[] b = new byte[1024];
        while ((i = inputStream.read(b))!= -1){
            System.out.println(new String(b,0,i));
        }
        System.out.println("客户端退出");
        //关闭流
        inputStream.close();
        outputStream.close();
        socket.close();
 
 
    }
}

小练习3

有了前面的示范，这题也很容易解决

利用Buffered 和转换流


public class Socket05 {
    public static void main(String[] args) throws IOException {
        //监听9999
        ServerSocket serverSocket = new ServerSocket(9999);
        //等待连接
        Socket socket = serverSocket.accept();
        InputStream inputStream = socket.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        String string = bufferedReader.readLine();
        System.out.println(string);
        //回信
        OutputStream outputStream = socket.getOutputStream();
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write("你也好，客户端");
        bufferedWriter.newLine();//换行表示输入结束
        bufferedWriter.flush();如果使用字符流一点要刷新，否则不能加入通道
        //关闭流
        socket.close();
        serverSocket.close();
        bufferedReader.close();
        bufferedWriter.close();
        System.out.println("服务端关闭");
    }
}


public class Socket06 {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket(InetAddress.getLocalHost(),9999);
        OutputStream outputStream = socket.getOutputStream();
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write("你好啊服务器");
        bufferedWriter.newLine();//换行表示输入结束
        bufferedWriter.flush();//如果使用字符流一点要刷新，否则不能加入通道
        //接收回信
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String string = bufferedReader.readLine();
        System.out.println(string);
        //关闭流
        bufferedReader.close();
        bufferedWriter.close();
        socket.close();
        System.out.println("服务端关闭");
 
    }
}

Natstat 指令

还有个 netstat -anb 可以显示哪个程序连接到这个端口

TCP网络通信小秘密

UDP网络通信编程

基础介绍

UDP小练习


 
public class UdpReceiverA {
    public static void main(String[] args) throws IOException {
        //1.创建一个DatagramSocket,准备在9999接收数据
        DatagramSocket datagramSocket = new DatagramSocket(9999);
        //2.构建一个 DatagramPacket对象，准备接收数据
        //UDP协议数据包最大64k 64*1024
        byte[] buf = new byte[64 * 1024];
        DatagramPacket datagramPacket = new DatagramPacket(buf, buf.length);
        //3.调用，接收方法,将通过网络传输的 DatagramPacket 对象
        datagramSocket.receive(datagramPacket);//在9999端口等待，如果有数据包传输，就接收
        //4.把Packet 进行拆包，取出数据并显示
        int len = datagramPacket.getLength();//实际接收到的数据字节长度
        byte[] data = datagramPacket.getData();//接收到的数据
        String s =new String(data,0,len);
        System.out.println(s);
        //回复消息
        byte[] bytes = "没问题，我去找你".getBytes();
        DatagramPacket datagramPacket1 = new DatagramPacket(bytes,bytes.length, InetAddress.getByName("192.168.43.237"),9998);
        datagramSocket.send(datagramPacket1);
        //5.关闭流
        datagramSocket.close();
    }
}


public class UdpSenderB {
    public static void main(String[] args) throws IOException {
        //1。创建DatagramPacket 对象，准备接收和发送数据
        DatagramSocket socket = new DatagramSocket(9998);//发送端也可以是接收端，如果
        //之后接收数据，就在9998端口接收
        //2.发送数据封转 DatagramPacket(数组，数组长度，对方ip地址，端口号)
        byte[] bytes = "hello,今天吃火锅".getBytes();
        DatagramPacket packet =
                new DatagramPacket(bytes,bytes.length, InetAddress.getByName("192.168.43.237"),9999);
        socket.send(packet);//发送封装后的数据
        //接收回信
        byte[] bytes1 = new byte[1024*5];//
        DatagramPacket datagramPacket = new DatagramPacket(bytes1, bytes1.length);
        int len = datagramPacket.getLength();
        socket.receive(datagramPacket);
        byte[] bytes2 = datagramPacket.getData();
        String s = new String(bytes2,0,len);
        System.out.println(s);
 
        socket.close();
    }
}

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原文地址：https://blog.csdn.net/hagong9/article/details/125995211

网络编程 笔记

域名和端口号

网络通讯协议

TCP和UDP

InetAddress类

网络多线程_Socket （套接字）

小练习

Natstat 指令

TCP网络通信小秘密

UDP网络通信编程

基础介绍

UDP小练习

网络编程笔记