Galaxy Note 5, Websites with custom ports do not work over WIFI

[AC Question]

I have bought a Galaxy Note 5 2 days ago and I can not access any website or application that uses a custom port when I am using Wi-Fi. I tried at different locations over different Wi-Fi networks and routers and it is not working. The custom website and port is working fine over any other device, just my Galaxy Note 5 has this problem. Also, it is working with my Galaxy Note 5 if I use mobile data or a VPN, the problem occurs only over Wi-Fi.
So, I typed (on both Internet and Chrome apps):
2.3.4.5:5000 (sample) and it is not working. If I turn off Wi-Fi and use mobile data it is working instantly.

I assume it is some kind of a firewall but I can't figure out from where this is coming. I even tried to start the phone on safe mode and the results are the same.

What can be wrong?

 

[BBgeeqed04]

Check your permissions? I had a similar issue and it was permissions for me.

 

[ZoltanB74]

Where should I check Permissions?

 

[BBgeeqed04]

Do you have Lollipop or Marshmallow? On Marshmallow, Settings>>Privacy and safety>>App permissions. I can't remember, but I believe it's the same on Lollipop.