This article explains how to simulate a web proxy connection on the P8.

1. SSH to the P8
   
2. Telnet <LAN IP of P8> 3128
   
3. Issue a connect statement "CONNECT <url>:443 HTTP/1.0". E.g CONNECT outlook.office365.com:443 HTTP/1.0
   
4. Hit 'enter' and 'enter" again.

You should see something similar to "HTTP/1.1 200 Connection established" if not the text returned will be indicative of the issue connecting to the website.