error 12, caused by the cliebt side - how?

[Eberhard Moenkeberg]

Hi,
I am seeing an rsync client reporting:

rsync: connection unexpectedly closed (9233023 bytes read so far)
rsync error: error in rsync protocol data stream (code 12) at io.c(342)

while the rsync server is saying:

Jan 27 19:57:18 ftp4 rsyncd[24334]: send ftp3.gwdg.de [134.76.12.3] pub () languages/perl/CPAN/indices/du-k.gz 32935
Jan 27 19:57:24 ftp4 rsyncd[24334]: send ftp3.gwdg.de [134.76.12.3] pub () languages/perl/CPAN/indices/find-ls.gz 2896911
Jan 27 22:39:15 ftp4 rsyncd[24334]: rsync: connection unexpectedly closed (37034 bytes received so far) [sender]
Jan 27 22:39:15 ftp4 rsyncd[24334]: rsync error: error in rsync protocol data stream (code 12) at io.c(359)
Jan 27 22:39:15 ftp4 rsyncd[24334]: rsync: writefd_unbuffered failed to write 76 bytes: phase "unknown" [sender]: Broken pipe (32)
Jan 27 22:39:15 ftp4 rsyncd[24334]: rsync error: error in rsync protocol data stream (code 12) at io.c(909)

What may be the cause of this fault, and why don't I see ANYTHING USEFUL 
on EITHER side?

Cheers -e
-- 
Eberhard Moenkeberg (emoenke at gwdg.de, em at kki.org)