ERR_TUNNEL_CONNECTION_FAILED on mobile network on android

For the past few days, whenever I tried to access any site with HTTPS, I used to get this error.

"This webpage is not available
ERR_TUNNEL_CONNECTION_FAILED"

This used to occur only on mobile network (airtel) and not on WiFi. At first it seemed to be a problem with chrome. But the same problem was there in other browsers. After breaking my head for a while I read somewhere that android doesn't support SSL over any port other than 443 (too weird to be true). But this couldn't be the issue because https://google.com , https://twitter.com etc use 443. 

Upon investigating further, I realized that it is a very silly issue. It is because the default Access Point (Airtel Live) that came with my carrier (airtel) had a proxy that was not allowing SSL Tunneling.

After setting Proxy and Port to nothing, the problem was solved!

(98)Address already in use: make_sock: could not bind to address 0.0.0.0:443

I was setting up SSL on localhost to get https://localhost. I was successfully able to get the digital signature, sign it. But when i restarted apache2 I was getting this error:

(98)Address already in use: make_sock: could not bind to address 0.0.0.0:443

This means that port was already being listened. Hence at first I tried to kill the processes which are using that port. When this didn't work I tried this:

open /etc/apache2/ports.conf

Remove the line outside any <IfModule> tag which says Listen 443

Problem solved!!