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javaurlhttpsurlconnection

Why server returns me the Response Code 403 for a valid file in java?

I want to get the Content Length of this file by java:

https://www.subf2m.co/subtitles/farsi_persian-text/SImp4fRrRnBK6j-u2RiPdXSsHSuGVCDLz4XZQLh05FnYmw92n7DZP6KqbHhwp6gfvrxazMManmskHql6va6XEfasUDxGevFRmkWJLjCzsCK50w1lwNajPoMGPTy9ebCC0&name=Q2FwdGFpbiBNYXJ2ZWwgRmFyc2lQZXJzaWFuIGhlYXJpbmcgaW1wYWlyZWQgc3VidGl0bGUgLSBTdWJmMm0gW3N1YmYybS5jb10uemlw

When I insert this url in Firefox or Google Chrome, it downloads a file. but when i want to see that file's size by Java HttpsURlConnection, server returns me Response Code 403 and Content Length -1. why this happens? Thanks

try {
  System.out.println("program started -----------------------------------------");
  String str_url = "https://www.subf2m.co/subtitles/farsi_persian-text/SImp4fRrRnBK6j-u2RiPdXSsHSuGVCDLz4XZQLh05FnYmw92n7DZP6KqbHhwp6gfvrxazMManmskHql6va6XEfasUDxGevFRmkWJLjCzsCK50w1lwNajPoMGPTy9ebCC0&name=Q2FwdGFpbiBNYXJ2ZWwgRmFyc2lQZXJzaWFuIGhlYXJpbmcgaW1wYWlyZWQgc3VidGl0bGUgLSBTdWJmMm0gW3N1YmYybS5jb10uemlw";
  URL url = new URL(str_url);
  HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
  con.setConnectTimeout(150000);
  con.setReadTimeout(150000);
  con.setRequestMethod("HEAD");
  con.setInstanceFollowRedirects(false);
  con.setRequestProperty("Accept-Encoding", "identity");
  con.setRequestProperty("connection", "close");
  con.connect();

  System.out.println("responseCode:  " + con.getResponseCode());
  System.out.println("contentLength:  " + con.getContentLength());
} catch (IOException e) {
  System.out.println("error | " + e.toString());
  e.printStackTrace();
}

output:

program started -----------------------------------------
responseCode:  403
contentLength:  -1
Solution

  • The default Java user-agent is blocked by some online services (most notably, Cloudflare). You need to set the User-Agent header to something else.

    con.setRequestProperty("User-Agent", "My-User-Agent");

    In my experience, it doesn't matter what you set it to, as long as it's not the default one:

    con.setRequestProperty("User-Agent", "aaa"); // works perfectly fine



    EDIT: looks like this site uses Cloudflare with DDoS protection active - your code won't run the JavaScript challenge needed to actually get the content of the file.