I don't understand your question :
- the server receive inventory from agent : look at apache log and 'activity.log'
- agents send inventory : look at 'agent log'
OCS Inventory is based on 'client server approch' : the agent (client) send inventory and server listen. Windows agent is a service, linux agent could run as daemon (=service) or coulb be launch by cron (better with random hour and minutes).
Windows agent log : %programdata%\OCS Inventory NG\Agent\ocsinventory.log (more data with debug=1 in ocsinventory.ini)
Linux agent log : file defined with variable 'logfile=' in /etc/ocsinventory/ocsinventory-agent.cfg (usually /var/log/ocsinventory-client/ocsinventory-agent.log) (more data with --debug ou debug=1 in cfg file).