I have 2 internet-connected 4G modems connected to 2 separate computers and I'd like to send/receive data between them with sockets (UDP) using the modems' packet-switched 4G Internet connection, not using AT commands to dial each other.
The problem is that I can't get either modem to receive incoming UDP traffic from the other. The provider is NAT'ing both devices and I can't do any port forwarding within the GSM provider's router. It looks like the GSM provider blocks incoming connections to both devices, so how can I do socket communication? I've thought about setting up a FTP/web/email server to relay traffic between the two devices, but I'd rather do it with socket (TCP or UDP). Any ideas?