Opsview has a daemon called import_ndologsd which reads NDO logs in /usr/local/nagios/var/ndologs and for each file, it invokes file2sock to push that to the ndo2db daemon.

Set /usr/local/nagios/etc/Log4perl.cfg and uncomment:

log4perl.logger.import_ndologsd=DEBUG

This can take upto 30 seconds to acknowledge, but there will be more debug in opsviewd.log and a copy of each ndolog will be copied into /usr/local/nagios/var/ndologs.archive.

This occurs when ndo is sending data to the ndo2db. Check the syslog files for more details. Has been seen when the database credentials have not been setup correctly - ndo2db will disconnect the connection at this point, rather than reading all the data. The error is a bit misleading, but is probably all the client can receive.