Lighttpd

For a project where I am one of the developers I am looking for a solution to log succesful downloads. I use mod_dirlisting to list the contents in a folder. People can download the files listed, and I am curious if I can log succesful downloads.

In mod_accesslog I have enabled some parameters that I think are useful, like connection status, bytes outgoing, physical filename, time used in seconds etc.

However, I see a lot of rows like:
FILENAME1 X 65431 1
FILENAME1 X 65431 1
FILENAME1 + 65431 1
FILENAME1 + 91222 1
FILENAME2 + 123211121 411
FILENAME2 + 123211121 450
FILENAME2 + 123211121 475

As you can see, I cannot use a simple SUM (which will result in 7 downloads) because in reality only two files were downloaded. In the lighttpd1 docs there is not much information about the different parameters. But in the lighttpd2 docs I saw that the connection status means "Connection status after response: “X” if aborted before completed, “+” if keepalive, “-” if no keepalive".

First I used the '+' status as a sign of a successful download, but as you can see the last 3 log rows are all '+' but still, it's only one request and one file. Also the time used is getting larger but the bytes stay the same.

So at this moment I am looking for some additional signs for a succesful download. I was thinking of maybe comparing the bytes outgoing with the amount of bytes of the original file, but this would create some additional scripts.

My question for now is: is there a simple way to detect a complete, unique, succesful download in lighttpd?