The questions related to IP traffic in cellular networks reached me.
Q: The other question about data transfer is about how cell phone
companies charge for data transmission. If I send a IP/UDP packet,
this will obviously be billed to me. But if somebody sends me an
IP/UDP packet will it be charged only if I receive it? Will it be
charged at all if it comes from another chip? What about broadcasted
A: You always pay. The cellular modules I am using offering a firewall wall. They will not answer by pinging them. The next is, that most cellular operators does not route IP packet from server in the Internet to your cellular module. Your cellular module has an internal non public IP address inside the cellular network. The next higher level of security is to route specific IP addresses to the cellular module only. Nevertheless, one German operator helps you with a public IP address that you can access from server in the Internet. Anybody can access to the cellular module. If you do not activate the firewall inside the cellular module, then end of the month you maybe get a high invoice for IP traffic.
Nevertheless, if you still have further questions and would like to start the development of your own cellular based IP application right now then just send an e-mail to harald.naumann (at) gsm-modem.de or use the form here. BTW, a consulting contract for one or two days can save you a lot of time and money. I will be glad to share our more than 15 years in GSM and GPS plus 25 years in radio communication with you. Even when I have no time left, then one of my business friends in wireless M2M will jump in.