scenario of wifi : i'm using wifi in hostel which having cyberoam firewall and all the computer which uses that access point. that access point have following configuration
default gateway : 192.168.100.1 primary dns server : 192.168.100.1
here, when i try to open a website the cyberoam firewall redirects the page to a login page (with correct login information, we can browse internet else not), and also website access and bandwidth limitations.
once i've heard about pd-proxy which finds open port and tunnels through a port ( usually udp 53). using pd-proxy with UDP 53 port, i can browse internet without login, even bandwidth limit is bypassed !!!
and another software called openvpn with connecting openvpn server through udp port 53 i can browse internet without even login into the cyberoam.
both of softwares uses port 53, specially openvpn with port 53, now i've a VPS server in which i can install openvpn server and connect through the VPS server to browse internet.
i know why that is happening because with pinging on some website(eb. google.com) it returns it's ip address that means it allows dns queries without login.
but the problem is there is already DNS service is running on the VPS server on port 53. and i can only use 53 port to bypass the limitations as i think. and i can not run openvpn service on my VPS server on port 53.
so how to scan the wifi for vulnerable ports like 53 so that i can figure out the magic port and start a openvpn service on VPS on the same port. ( i want to scan similar vulnerable ports like 53 on cyberoam in which the traffic can be tunneled, not want to scan services running on ports).
improvement of the question with retags and edits are always welcomed...
i'ave made simple client server application in which a external computer acts as server running on UDP port 53 and client running inside the wifi; will connnect to that out side server that is running on UDP port 53. problem is it can't connect that server application. what should be the reason, why client inside wifi can't connect outside server running on UDP port 53 ?
NOTE : all these are for Educational purpose only, i'm curious about network related knowledge.....