The only hint you'll likely be able to get is the reported download size. The log should say something like 
#ip address  ...  request                   status code  size  ...
10.10.10.10  ...  "GET /your/file HTTP/1.0" 200          65536  ...

[download]
The "size" field gives you the bytes sent. If the connection was broken mid-way, that value will be lower than your file size.

See Apache access log for the full details.

In reply to Re^5: File download tool, file size issues, cgi-application by rhesa
in thread File download tool, file size issues, cgi-application by cupojoe

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