Implement pause/resume in file downloading

Okay problem fixed, here is my code for other users who wants to implement pause/resume:

        if (outputFileCache.exists())
        {
            connection.setAllowUserInteraction(true);
            connection.setRequestProperty("Range", "bytes=" + outputFileCache.length() + "-");
        }

        connection.setConnectTimeout(14000);
        connection.setReadTimeout(20000);
        connection.connect();

        if (connection.getResponseCode() / 100 != 2)
            throw new Exception("Invalid response code!");
        else
        {
            String connectionField = connection.getHeaderField("content-range");

            if (connectionField != null)
            {
                String[] connectionRanges = connectionField.substring("bytes=".length()).split("-");
                downloadedSize = Long.valueOf(connectionRanges[0]);
            }

            if (connectionField == null && outputFileCache.exists())
                outputFileCache.delete();

            fileLength = connection.getContentLength() + downloadedSize;
            input = new BufferedInputStream(connection.getInputStream());
            output = new RandomAccessFile(outputFileCache, "rw");
            output.seek(downloadedSize);

            byte data[] = new byte[1024];
            int count = 0;
            int __progress = 0;

            while ((count = input.read(data, 0, 1024)) != -1 
                    && __progress != 100) 
            {
                downloadedSize += count;
                output.write(data, 0, count);
                __progress = (int) ((downloadedSize * 100) / fileLength);
            }

            output.close();
            input.close();
       }

It is impossible to tell what is wrong without some more information, however things to note:

1. You must make a HTTP/1.1 request (it's hard to tell from your sample code)
2. The server must support HTTP/1.1
3. The server will tell you what it supports with an Accept-Ranges header in the response
4. If-Range should be the etag the server gave you for the resource, not the last modified time

You should check your range request with something simple to test the origin actually supports the Range request first (like curl or wget )

It nay be that your server is taking to long to respond (more then the timeout limit) or this is also a fact that not all servers support pause - resume. It is also a point to ponder that weather the file is downloaded through Http, https, ftp or udp.

Pausing" could just mean reading some of the stream and writing it to disk. When resuming you would have to use the headers to specify what is left to download.

you may try something like :

 HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    if(ISSUE_DOWNLOAD_STATUS.intValue()==ECMConstant.ECM_DOWNLOADING){
         File file=new File(DESTINATION_PATH);
        if(file.exists()){
             downloaded = (int) file.length();
         connection.setRequestProperty("Range", "bytes="+(file.length())+"-");
    }
}else{
    connection.setRequestProperty("Range", "bytes=" + downloaded + "-");
}
connection.setDoInput(true);
connection.setDoOutput(true);
progressBar.setMax(connection.getContentLength());
 in = new BufferedInputStream(connection.getInputStream());
 fos=(downloaded==0)? new FileOutputStream(DESTINATION_PATH): new FileOutputStream(DESTINATION_PATH,true);
 bout = new BufferedOutputStream(fos, 1024);
byte[] data = new byte[1024];
int x = 0;
while ((x = in.read(data, 0, 1024)) >= 0) {
    bout.write(data, 0, x);
     downloaded += x;
     progressBar.setProgress(downloaded);
}

and please try to sync things.