通过代理 Java 创建套接字

Question

我已经编写了代码，必须通过套接字使用 http HEAD 请求找到文件大小......我在家里尝试使用非代理连接它的工作......但是当我在我的大学里尝试使用IP为172.16.4.6和端口1117的代理服务器时，它不起作用......任何建议...谢谢。

public class Proxytesting {
    private static OutputStream os;
    private static InputStream in;
    private static BufferedReader reader;
    private static int Totalsize;

    public static void main(String[] args) {
        try {         
            URL url_of_file=new URL("http://www.stockvault.net/data/s/124348.jpg");
            String hostaddress=url_of_file.getHost();
            ////////////////////for proxy server ///////////////////
            String textip="172.16.4.7";
            InetAddress host=InetAddress.getByName(textip);
            System.out.println(host);
            int port=1117;
            SocketAddress ad=new InetSocketAddress(host, 1117);
            Proxy proxy = new Proxy(Proxy.Type.SOCKS, ad);
            Socket mysocket2 = new java.net.Socket();
            mysocket2.connect(new InetSocketAddress(hostaddress,80));
            System.out.println("Socket opened to " + hostaddress + "n");
            String file=url_of_file.getFile();
            System.out.println(" file = "+file);
            os = mysocket2.getOutputStream();
            String headRequest = "HEAD " +url_of_file+" HTTP/1.1rn"
                     + "Host: "+ hostaddress +"rnrn";
            os.write(headRequest.getBytes());
            in = mysocket2.getInputStream();
            reader= new BufferedReader(new InputStreamReader(in));
            String contlength="Content-Length:";
            // 1. Read the response header from server separately beforehand.
            String response;
            Totalsize = 0;
            do{ 
                response = reader.readLine();
                if(response.indexOf("Content-Length") > -1)
                {            
                    Totalsize = Integer.parseInt(response.substring(response.indexOf(' ')+1)); 
                    response = null;
                }
            }while(response != null);  
            System.out.println(" cont_lentht ##### == "+Totalsize);
    } catch (IOException ex) {
        Logger.getLogger(Proxytesting.class.getName()).log(Level.SEVERE, null, ex);
    }

我得到的错误是：

Unknown host exception at for code [ mysocket2.connect(
    new InetSocketAddress(hostaddress,80));]

Answer 1

你给自己带来了很大的困难。 使用 HttpURLConnection 通过代理进行连接：

HttpConnection conn = (HttpConnection) url_of_file.openConnection(proxy);
conn.setRequestMethod("HEAD");
Totalsize = conn.getContentLength();

还有其他 HTTP 客户端做得更好，但除非现有客户端没有满足您的需求，否则您不应该创建自己的客户端！

Answer 2

感谢您在评论中的线索。我找到了问题的解决方案。 我使用错误的端口构建InetSocketAddress两次的代码中存在错误。 完整的工作代码如下。

public class Proxytesting {
    private static OutputStream os;
    private static InputStream in;
    private static BufferedReader reader;
    private static int Totalsize;
    public static void main(String[] args) {
        try {         
            URL url_of_file=new URL("http://www.stockvault.net/data/s/124348.jpg");
            String hostaddress=url_of_file.getHost();
            ////////////////////for proxy server ///////////////////
            String textip="172.16.4.7";
            InetAddress host=InetAddress.getByName(textip);
            System.out.println(host);
            int port=1117;
            SocketAddress ad=new InetSocketAddress(host, 1117);
            Proxy proxy = new Proxy(Proxy.Type.SOCKS, ad);
            Socket mysocket2 = new java.net.Socket();
            mysocket2.connect(ad);
            System.out.println("Socket opened to " + hostaddress + "n");
            String file=url_of_file.getFile();
            System.out.println(" file = "+file);
            os = mysocket2.getOutputStream();
            String headRequest = "HEAD " +url_of_file+" HTTP/1.1rn"
                     + "Host: "+ hostaddress +"rnrn";
            os.write(headRequest.getBytes());
            in = mysocket2.getInputStream();
            reader= new BufferedReader(new InputStreamReader(in));
            String contlength="Content-Length:";
            // 1. Read the response header from server separately beforehand.
            String response;
            Totalsize = 0;
            do{ 
                response = reader.readLine();
                if(response.indexOf("Content-Length") > -1)
                {            
                    Totalsize = Integer.parseInt(response.substring(response.indexOf(' ')+1)); 
                    response = null;
                }
            }while(response != null);  
            System.out.println(" cont_lentht ##### == "+Totalsize);
    } catch (IOException ex) {
        Logger.getLogger(Proxytesting.class.getName()).log(Level.SEVERE, null, ex);
    }