实例-Java 网络实例

获取指定主机的IP地址

import java.net.InetAddress;
import java.net.UnknownHostException;

public class GetIP {
   public static void main(String[] args) {
      InetAddress address = null;
      try {
         address = InetAddress.getByName
         ("www.w3cschool.cc");
      }
      catch (UnknownHostException e) {
         System.exit(2);
      }
      System.out.println(address.getHostName() + "="
      + address.getHostAddress());
      System.exit(0);
   }
}

结果：

www.w3cschool.cc=222.73.134.120

---

查看端口是否已使用

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

public class Main {
   public static void main(String[] args) {
      Socket Skt;
      String host = "localhost";
      if (args.length > 0) {
         host = args[0];
      }
      for (int i = 0; i < 1024; i++) {
         try {
            System.out.println("查看 "+ i);
            Skt = new Socket(host, i);
            System.out.println("端口 " + i + " 已被使用");
         }
         catch (UnknownHostException e) {
            System.out.println("Exception occured"+ e);
            break;
         }
         catch (IOException e) {
         }
      }
   }
}

结果：

……
查看 17
查看 18
查看 19
查看 20
查看 21
端口 21 已被使用
查看 22
查看 23
查看 24
……

---

获取本机ip地址及主机名

import java.net.InetAddress;

public class Main {
   public static void main(String[] args) 
   throws Exception {
      InetAddress addr = InetAddress.getLocalHost();
      System.out.println("Local HostAddress: 
      "+addr.getHostAddress());
      String hostname = addr.getHostName();
      System.out.println("Local host name: "+hostname);
   }
}

结果：

Local HostAddress: 192.168.1.159
Local host name: harsh

---

获取远程文件大小

import java.net.URL;
import java.net.URLConnection;

public class Main {
   public static void main(String[] argv) 
   throws Exception {
      int size;
      URL url = new URL("http://www.w3cschool.cc/wp-content/themes/w3cschool.cc/assets/img/newlogo.png");
      URLConnection conn = url.openConnection();
      size = conn.getContentLength();
      if (size < 0)
      System.out.println("无法获取文件大小。");
      else
      System.out.println("文件大小为：" +
      + size + " bytes");
      conn.getInputStream().close();
   }
}

结果：

文件大小为：4261 bytes

---

Socket 实现多线程服务器程序

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

public class MultiThreadServer implements Runnable {
   Socket csocket;
   MultiThreadServer(Socket csocket) {
      this.csocket = csocket;
   }

   public static void main(String args[]) 
   throws Exception {
      ServerSocket ssock = new ServerSocket(1234);
      System.out.println("Listening");
      while (true) {
         Socket sock = ssock.accept();
         System.out.println("Connected");
         new Thread(new MultiThreadServer(sock)).start();
      }
   }
   public void run() {
      try {
         PrintStream pstream = new PrintStream
         (csocket.getOutputStream());
         for (int i = 100; i >= 0; i--) {
            pstream.println(i + 
            " bottles of beer on the wall");
         }
         pstream.close();
         csocket.close();
      }
      catch (IOException e) {
         System.out.println(e);
      }
   }
}

结果：

Listening
Connected

---

查看主机指定文件的最后修改时间

import java.net.URL;
import java.net.URLConnection;

public class Main {
   public static void main(String[] argv) 
   throws Exception {
      URL u = new URL("http://127.0.0.1/java.bmp");
      URLConnection uc = u.openConnection();
      uc.setUseCaches(false);
      long timestamp = uc.getLastModified();
      System.out.println("java.bmp 文件最后修改时间 :"+timestamp);
   }
}

结果：

java.bmp 文件最后修改时间 24 May 2014 12:14:50

---

使用 Socket 连接到指定主机

import java.net.InetAddress;
import java.net.Socket;

public class WebPing {
   public static void main(String[] args) {
      try {
         InetAddress addr;
         Socket sock = new Socket("www.w3cschool.cc", 80);
         addr = sock.getInetAddress();
         System.out.println("连接到 " + addr);
         sock.close();
      } catch (java.io.IOException e) {
         System.out.println("无法连接 " + args[0]);
         System.out.println(e);
      }
   }
}

结果：

连接到 http:/www.w3cschool.cc/222.73.134.120

---

网页抓取

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.net.URL;

public class Main {
   public static void main(String[] args) 
   throws Exception {
      URL url = new URL("http://www.w3cschool.cc");
      BufferedReader reader = new BufferedReader
      (new InputStreamReader(url.openStream()));
      BufferedWriter writer = new BufferedWriter
      (new FileWriter("data.html"));
      String line;
      while ((line = reader.readLine()) != null) {
         System.out.println(line);
         writer.write(line);
         writer.newLine();
      }
      reader.close();
      writer.close();
   }
}

结果：

<!DOCTYPE html> <html> <head> <meta charset="UTF-8"/> <meta http-equiv="X-UA-Compatible" content="IE=11,IE=10,IE=9,IE=8"/>……

---

获取 URL响应头的日期信息

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Date;

public class Main{
   public static void main(String args[]) 
   throws Exception {
      URL url = new URL("http://www.w3cschool.cc");
      HttpURLConnection httpCon = 
      (HttpURLConnection) url.openConnection();
      long date = httpCon.getDate();
      if (date == 0)
      System.out.println("无法获取信息。");
      else
      System.out.println("Date: " + new Date(date));
   }
}

结果：

Date: Mon May 04 11:57:06 CST 2015

---

* 获取 URL 响应头信息*

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;
import java.util.Set;

public class Main {
    public static void main(String[] args) throws IOException{
        URL url = new URL("http://www.w3cschool.cc");
        URLConnection conn = url.openConnection();

        Map headers = conn.getHeaderFields();
        Set<String> keys = headers.keySet();
        for( String key : keys ){
            String val = conn.getHeaderField(key);
            System.out.println(key+"    "+val);
        }
        System.out.println( conn.getLastModified() );
    }
} 

结果：

Transfer-Encoding    chunked
null    HTTP/1.1 200 OK
Server    Tengine/1.3.0
Connection    keep-alive
Vary    Cookie
Date    Mon, 04 May 2015 03:54:05 GMT
X-Pingback    http://www.w3cschool.cc/xmlrpc.php
X-Powered-By    PHP/5.3.15
Content-Type    text/html; charset=UTF-8

---

解析 URL

import java.net.URL;

public class Main {
   public static void main(String[] args) 
   throws Exception {
      URL url = new URL("http://www.w3cschool.cc/html/html-tutorial.html");
      System.out.println("URL 是 " + url.toString());
      System.out.println("协议是 " 
      + url.getProtocol());
      System.out.println("文件名是 " + url.getFile());
      System.out.println("主机是 " + url.getHost());
      System.out.println("路径是 " + url.getPath());
      System.out.println("端口号是 " + url.getPort());
      System.out.println("默认端口号是 " 
      + url.getDefaultPort());
   }
}

结果：

URL 是 http://www.w3cschool.cc/html/html-tutorial.html
协议是 http
文件名是 /html/html-tutorial.html
主机是 www.w3cschool.cc
路径是 /html/html-tutorial.html
端口号是 -1
默认端口号是 80

---

ServerSocket 和 Socket 通信实例

1、建立服务器端

• 服务器建立通信ServerSocket
• 服务器建立Socket接收客户端连接
• 建立IO输入流读取客户端发送的数据
• 建立IO输出流向客户端发送数据消息

服务器代码：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
   public static void main(String[] args) {
      try {
         ServerSocket ss = new ServerSocket(8888);
         System.out.println("启动服务器....");
         Socket s = ss.accept();
         System.out.println("客户端:"+s.getInetAddress().getLocalHost()+"已连接到服务器");

         BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
         //读取客户端发送来的消息
         String mess = br.readLine();
         System.out.println("客户端："+mess);
         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
         bw.write(mess+"\n");
         bw.flush();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

结果：

启动服务器....

2、建立客户端

• 创建Socket通信，设置通信服务器的IP和Port
• 建立IO输出流向服务器发送数据消息
• 建立IO输入流读取服务器发送来的数据消息

客户端代码：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class Client {
   public static void main(String[] args) {
      try {
         Socket s = new Socket("127.0.0.1",8888);

         //构建IO
         InputStream is = s.getInputStream();
         OutputStream os = s.getOutputStream();

         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
         //向服务器端发送一条消息
         bw.write("测试客户端和服务器通信，服务器接收到消息返回到客户端\n");
         bw.flush();

         //读取服务器返回的消息
         BufferedReader br = new BufferedReader(new InputStreamReader(is));
         String mess = br.readLine();
         System.out.println("服务器："+mess);
      } catch (UnknownHostException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

结果：

服务器：测试客户端和服务器通信，服务器接收到消息返回到客户端