How to find torrent name

That depends:

If you have the packets where someone is loading the torrent description file (usually via web browser or via magnet link), you can find the file name inside that file. A file format description can be found on the internet, e.g. at Wikipedia: http://en.wikipedia.org/wiki/Torrent_file. It won't work if the description file is transferred via HTTPS, of course.

If the torrent program is already loading the actual content, then no, I don't think you can. Nowadays, in most cases torrent transfers are also encrypted for obvious reasons, so you'll only see meaningless bytes being transferred on whatever port the torrent program uses.