获取本机外网IP地址（External IP Address）示例

我就是我 2022-06-13 13:52 320阅读 0赞

原文：[http://www.cnblogs.com/Csharpblogs/articles/2218156.html][http_www.cnblogs.com_Csharpblogs_articles_2218156.html]

import java.io.IOException;
    import java.io.InputStream;
    import java.net.HttpURLConnection;
    import java.net.MalformedURLException;
    import java.net.URL;
    import java.util.regex.Matcher;
    import java.util.regex.Pattern;
    
    /**
     * 获取本机外网IP地址
     * 思想是访问网站http://checkip.dyndns.org/，得到返回的文本后解析出本机在外网的IP地址
     * @author Administrator
     *
     */
    public class ExternalIpAddressFetcher {
        // 外网IP提供者的网址
        private String externalIpProviderUrl;
    
        // 本机外网IP地址
        private String myExternalIpAddress;
    
        public ExternalIpAddressFetcher(String externalIpProviderUrl) {
            this.externalIpProviderUrl = externalIpProviderUrl;
    
            String returnedhtml = fetchExternalIpProviderHTML(externalIpProviderUrl);
            
            parse(returnedhtml);
        }
    
        /**
         * 从外网提供者处获得包含本机外网地址的字符串
         * 从http://checkip.dyndns.org返回的字符串如下
         * <html><head><title>Current IP Check</title></head><body>Current IP Address: 123.147.226.222</body></html>
         * @param externalIpProviderUrl
         * @return
         */
        private String fetchExternalIpProviderHTML(String externalIpProviderUrl) {
            // 输入流
            InputStream in = null;
            
            // 到外网提供者的Http连接
            HttpURLConnection httpConn = null;
    
            try {
                // 打开连接
                URL url = new URL(externalIpProviderUrl);
                httpConn = (HttpURLConnection) url.openConnection();
                            
                // 连接设置
                HttpURLConnection.setFollowRedirects(true);
                httpConn.setRequestMethod("GET");
                httpConn.setRequestProperty("User-Agent",
                        "Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");
    
                // 获取连接的输入流
                in = httpConn.getInputStream();
                byte[] bytes=new byte[1024];// 此大小可根据实际情况调整
                
                // 读取到数组中
                int offset = 0;
                int numRead = 0;
                while (offset < bytes.length
                       && (numRead=in.read(bytes, offset, bytes.length-offset)) >= 0) {
                    offset += numRead;
                }
                
                // 将字节转化为为UTF-8的字符串        
                String receivedString=new String(bytes,"UTF-8");
                
                // 返回
                return receivedString;
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    in.close();
                    httpConn.disconnect();
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
    
            // 出现异常则返回空
            return null;
        }
        
        /**
         * 使用正则表达式解析返回的HTML文本,得到本机外网地址
         * @param html
         */
        private void parse(String html){
            Pattern pattern=Pattern.compile("(\\d{1,3})[.](\\d{1,3})[.](\\d{1,3})[.](\\d{1,3})", Pattern.CASE_INSENSITIVE);    
            Matcher matcher=pattern.matcher(html);        
            while(matcher.find()){
                myExternalIpAddress=matcher.group(0);
            }    
        }    
    
        /**
         * 得到本机外网地址,得不到则为空
         * @return
         */
        public String getMyExternalIpAddress() {
            return myExternalIpAddress;
        }
        
        public static void main(String[] args){
            ExternalIpAddressFetcher fetcher=new ExternalIpAddressFetcher("http://checkip.dyndns.org/");
            
            System.out.println(fetcher.getMyExternalIpAddress());
        }
    }

[http_www.cnblogs.com_Csharpblogs_articles_2218156.html]: http://www.cnblogs.com/Csharpblogs/articles/2218156.html