As you might remember, last month before the demo I had a weird problem where my Gembird power strip application was malfunctioning. In short, the power strip connects to the Internet, and on my cell phone I configured an application where I can remotely switch on/off sockets on the power strip. The problem was that for some reason I could only connect to the power strip when i was on the same WLAN. Otherwise, the application said that the device was offline about 30 minutes after I would leave home. I thought that it was an application/faulty unit problem until today. I have 4 of those power strips so i swapped the faulty one and configured another gembird. I logged out from my wifi and used normal Internet access on my phone. Sure enough, the app died after an hour. But I noticed a weird thing: the app started working again as soon as i connected to the same wifi that the power strip was on! So I figured it wasn’t a problem with the connection between the power strip and the cloud server, but rather between my phone and the cloud server! It appears that the connection is to the TCP port 5000 of the Gembird cloud server, which i guess is blocked by the ISP. However, if I use wifi at home to use the gembird app, the status is OK.
I wouldn’t actually be able to figure this out if it weren’t for the problem I had at work recently, where Meraki VPN site to site (their ”punching UDP holes” vpn where nobody has a public IP address) would only work on the landline internet, but it would fail if operating in 4g mode.
Internet access offered by mobile operators is not full (they only proxy some ports or simply block certain ports) or broken due to the way they do NAT. And I figure that IPv6 will solve all such problems.