Is there any way to actually communicate between two android devices over internet without having to have any service between the two devices?
Like posting something to device2 from device1 without having to “middle-land” on any other server or whatever?
Another question: I tried to ping my phone over the internet (simply using the IP address), which didn’t work, since it seems like my ISP shares the same WAN-IP for all the phones or at least a few of them. So is there any way to actually ping or send data to my specific phone just by using the IP or my Google account or something?
Almost all the end user devices are behind a ISP’s router, and many of them behind a lot devices in network hierarchy; Thus it is exceptionally rare that an end user device has public IP address.
Even if you want to run a public request listening server, you don’t have to get public IP address for your device, rather a redirect is created at the router, which redirects certain requests to your device.
Having that said, you cannot communicate between two end devices using internet without a public server in-between them.
So your possible solution could be: (If you don’t want to use an in-between server), you can send data using mms directly to mobile number.