Not sure what you mean by offline. PS3 Media Server is all local network traffic (other than web streaming) so a little confused what you mean.
You can enable the ip filter in PMS.
Enter the ip of your PS3 into the "
Use an IP filter" box on the General Configuration tab.....
For example...
Use an IP filter: 192.168.0.145 <-------example
Your PS3 would then be the only renderer/device able to access your PS3 Media Server and it's shared folders. This would secure your PMS to only your PS3, but your PC might show up on the local network. Folders visible there are beyond the scope of PMS and your responsibility to secure.
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If you need to direct connect your PS3, you can do it with just a plain old
Cat5e ethernet cable and
Internet Connection Sharing set up. This would use your WiFi NIC of your PC to connect to the internet and your local network, but have a direct ethernet to ethernet connection between your PS3 and PC. This would allow a secure connection between your PS3 and your PC.
If you have more than one ethernet adapter on the PC, even better.
Set up ICS thru Windows. Set your PC wifi up like normal then, connect a Cat5e cable from PC - PS3 then set up ip's as follows in this link......
viewtopic.php?f=6&t=4086&start=0#p18155Media streaming works very well this way as it's direct wired, but I have no idea how well ICS works as far as PS3 online thru your PC wifi adapter.