Java网络

网络

InetAddress类

• 获取本机InetAddress对象：getLocalHost()
• 根据指定主机名/域名获取ip地址对象：getByName()
• 获取InetAddress对象的主机名：getHostName()
• 获取InetAddress对象的地址：getHostAddress()

public class API_ {
    public static void main(String[] args) throws UnknownHostException {
        InetAddress localHost = InetAddress.getLocalHost();
        System.out.println(localHost);

        InetAddress byName = InetAddress.getByName("MaxLifetime-LAPTOP");
        System.out.println(byName);

        String lh1 = localHost.getHostName();
        System.out.println(lh1);

        String hm = byName.getHostName();
        System.out.println(hm);
    }
}

Socket

1. 套接字(Socket)开发网络应用程序被广泛采用，以至于成为事实上的标准

2. 通信的两端都要有插座，是两台机器间通信的端点

3. 网络通信其实就是Socket间的通信.

4. Socket允许程序把网络连接当成一个流，数据在两个套接字间通过IO传输

5. 一般主动发起通信的应用程序属客户端，等待通信请求的为服务端

TCP网络通信编程

1. 基本介绍
   • 基于客户端——服务端的网络通信
   • 底层使用的是TCP/IP协议
   • 应用场景举例：客户端发送数据、服务端接受并显示
   • 基于Socket的TCP编程
   • （可靠）

UDP编程

（不可靠）

练习1.：

1.编写一个服务器端,和一个客户端
2.服务器端在 9999端口监听
3.客户端连接到服务器端，发送“hello,server”，然后退出
4.服务器端接收到 客户端发送的 信息，输出，并退出

思路：

Server:

package Internet.API;




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

public class SocketTCPServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(9999);
        System.out.println("等待连接");
        Socket socket = serverSocket.accept();

        InputStream inputStream = socket.getInputStream();

        byte[] bytes = new byte[8];
        int readLen  = 0;
        while((readLen = inputStream.read(bytes)) != -1){
            System.out.print(new String(bytes ,0,readLen));
        }
        System.out.println();
        System.out.println("关闭");
        serverSocket.close();
        inputStream.close();
    }
}

Client：

package Internet.API;

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

public class SocketTCPClient {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        String string = "Hello world";

        OutputStream outputStream = socket.getOutputStream();
        byte[] bytes = new byte[8];

        outputStream.write(string.getBytes());

        outputStream.close();
        socket.close();
        }
    }

练习2：(使用字节流)

1. 编写一个服务端，和一个客户端
2. 服务器端在9999端口监听
3. 客户端连接到服务器端，发送“你好，服务器”，并接收服务器端回发的“你好，客户”再退出
4. 服务器端接收到客户端发送的信息，输出，并发送“你好，客户”，再退出

思路：

/+ 以上思路

Server:

package Internet.API.TCP_2;

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

public class SocketTCP2Server {
    public static void main(String[] args) throws IOException {
        //2.服务器端在9999端口监听
        ServerSocket serverSocket = new ServerSocket(9999);
        Socket socket = serverSocket.accept();
        InputStream inputStream = socket.getInputStream();
        byte[] bytes = new byte[1024];
        int readLen = 0;
        while((readLen = inputStream.read(bytes)) != -1){
            System.out.print(new String(bytes,0,readLen));
        }

        System.out.println("\nServer收到“你好，服务器”");


        //3.客户端连接到服务器端，发送“你好，服务器”，并接收服务器端回发的“你好，客户”再退出
        //4.服务器端接收到客户端发送的信息，输出，并发送“你好，客户”，再退出
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("你好，客户".getBytes());
        socket.shutdownOutput();

        serverSocket.close();
        socket.close();
        inputStream.close();
        outputStream.close();

    }
}

Client:

package Internet.API.TCP_2;

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

public class SocketTCP2Client {
    public static void main(String[] args) throws IOException {
        //3.客户端连接到服务器端，发送“你好，服务器”，并接收服务器端回发的“你好，客户”再退出
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("你好，服务器".getBytes());
        socket.shutdownOutput();


        InputStream inputStream = socket.getInputStream();
        byte[] bytes = new byte[1024];
        int readLen = 0;
        while((readLen = inputStream.read(bytes)) != -1){
            System.out.print(new String(bytes,0,readLen));
        }

        //4.服务器端接收到客户端发送的信息，输出，并发送“你好，客户”，再退出
        socket.close();
        outputStream.close();
        inputStream.close();
    }
}

练习3：(使用字节流)

1. 编写一个服务端，和一个客户端
2. 服务器端在9999端口监听
3. 客户端连接到服务器端，发送“你好，服务器”，并接收服务器端回发的“你好，客户”再退出
4. 服务器端接收到客户端发送的信息，输出，并发送“你好，客户”，再退出

Client:

package Internet.API.TCP_3;

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;

public class SocketTCP3Client {
    public static void main(String[] args) throws IOException {
        //3.客户端连接到服务器端，发送“你好，服务器”，并接收服务器端回发的“你好，客户”再退出
        Socket socket = new Socket(InetAddress.getLocalHost(), 9999);
        OutputStream outputStream = socket.getOutputStream();
        //使用字符流
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write("hello Server");
        bufferedWriter.newLine();
        bufferedWriter.flush();
        socket.shutdownOutput();


        InputStream inputStream = socket.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        String s = bufferedReader.readLine();
        System.out.println(s);

        //4.服务器端接收到客户端发送的信息，输出，并发送“你好，客户”，再退出
        socket.close();
        outputStream.close();
        bufferedReader.close();
        bufferedWriter.close();
    }
}

Server:

package Internet.API.TCP_3;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class SocketTCP3Server {
    public static void main(String[] args) throws IOException {
        //2.服务器端在9999端口监听
        ServerSocket serverSocket = new ServerSocket(9999);
        Socket socket = serverSocket.accept();
        InputStream inputStream = socket.getInputStream();

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        String s = bufferedReader.readLine();
        System.out.println(s);

        System.out.println("\nServer收到“你好，服务器”");


        //3.客户端连接到服务器端，发送“你好，服务器”，并接收服务器端回发的“你好，客户”再退出
        //4.服务器端接收到客户端发送的信息，输出，并发送“你好，客户”，再退出
        OutputStream outputStream = socket.getOutputStream();
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
        bufferedWriter.write("Hello Client");
        bufferedWriter.newLine();
        bufferedWriter.flush();

        serverSocket.close();
        socket.close();
        bufferedWriter.close();
        bufferedReader.close();
    }
}