[asterisk-users] Do public wifi block IAX port 4569

[Joseph]

I've installed zoiper on my old phone and it works on my private network over wifi.
I'm using standard IAX port 4569, so this port is open on my firewall.

But when I catch open wifi network in a mall or a Tim Horton "zoiper" fail to register.

Do they block IAX port 4569 or IAX protocol?

-- 
Joseph