HttpURLConnection slow to disconnect - Java / Android

Question

I want to get the file size of a file on a remote connection without actually downloading the (large) file. I am using the "Content-Length" header of the file. The relevant code is:

URL obj = new URL(FILES_URL + fileName);

String contentLength = "";
HttpURLConnection conn = null;

try {
    conn = (HttpURLConnection) obj.openConnection();
    conn.setConnectTimeout(3000);
    conn.setReadTimeout(3000);
    contentLength = conn.getHeaderField("Content-Length");
    int responseCode = conn.getResponseCode();
    Log.d(TAG, "responseCode: " + responseCode);
} finally {
    Log.d(TAG, "pre-disconnect");
    if (conn!=null) conn.disconnect();
    Log.d(TAG, "post-disconnect");
}

return contentLength;

The command "conn.disconnect();" sometimes seems to take forever. I have seen 23 seconds! Admittedly, this is connecting to a secondary local device which is running a web server, but the WiFi signal is strong, relatively fast, and I have never had any such problems using "curl" from my laptop. I do not have control over the web server I am connecting too.

The problem possibly is enhanced when making multiple similar connections to different files one after another, not sure. This is, however, creating entirely new HttpURLConnection's and not reusing the old one. Could reusing the connection help?

I never actually download the file or access the inputstream.

I could just not call disconnect, but I understand it is not recommended because resources would not be released. Is this not correct? I notice URLConnection doesn't have a disconnect. It is just suggested to close any streams you open.

This code is in an asynctask. I guess I could try moving the disconnect call itself to a further asynctask because I don't do anything afterwards. Not sure if that is even possible.

Do you have any suggestions? Should I try something other than HttpURLConnection to get the file size without downloading the file?

Answer 1

Thanks to EJP in the comments. Changing the request method to "HEAD" made the disconnect almost instantaneous:

conn.setRequestMethod("HEAD");

From what I have read, HttpURLConnection.disconnect() will skip through the entire response object if it hasn't been read. Therefore, for very large files, it will take a long time. Using the request method "HEAD" force the response body to be empty and solves the issue.