sim300 gprs connections problem

[albualex]

Hello, i am working on a project and i am using SIM300Z. The main ideea is that i am using a SIM300 as server and i have multiple connection. The problem is that i don't know how to communicate with all the clients simultaneously, beacause i can send data only at the last connected client.

Please help me! Thank you.

 

[pisoiu]

I think you can't. The modem will allow only one TCP connection at a time, aka one client served. This is the limitation of the integrated TCP stack.
If you need more clients, I'm afraid you have to implement a TCP stack with multiple sockets capability (in an external MCU), all by yourself. It is not an easy task, you have to write all stack starting from PPP, and ending with HTTP.
Another problem would be the allocation for a real IP address. Be really careful, the IP address you see when you attach to GPRS context is not always real. It happened to me when testing with Orange.

 

[albualex]

i can have multiple connection if i use UDP? and why when i set my sim300 as server, i can connect using TCP but using UDP the sim300 send nothing on serial?

thank you

 

[pisoiu]

Well, to be honest I've never used UDP, so I don't know what to say.