gprs - udp

[x!nDy]

Hi. Is anybody here familiar with gprs? I have a Siemens mc55i module, and I incorporate it with a pic18f4525. How can I bind the gprs module to a certain port so that it will accept incoming data from the server using UDP ? It works fine if I use TCP but if I use UDP, the module can send data to the server but it can't receive data from the server. I don't know what's wrong. Please help.

[libor]

It is quite possible that the GSM operator company's routers are not allowing inbound UDP traffic.
A GRPS device on a GSM network is usually hidden behind a NAT router with no own public IP address, just a proxy IP address leased for the time of a single TCP connection on a temporary basis. UDP is a connectionless protocol so there's no way a NAT router can map one of its public IP address (you might have addressed the data packet to) to your device's local IP address in the GSM network.

In my company we operate some industrial control devices with GPRS modems, we had to make a special subscription package with the GSM operator to bind a dedicated public IP address to the GPRS devices to allow them to receive inbound datagrams at any time. A "normal" GPRS subscription sold for web-surfing usually cannot work this way.

[x!nDy]

Hi. Thanks for the reply. I guess that seems to be the case since no matter what I do I can't really make it work. Anyway, I found a work around by using two protocols, UDP and TCP. Thanks.