[SOLVED] SIM5300E 3G UDP transmission issue

[serkam]

Hi

I am testing SIMCOM 3G SIM5300E that replaced SIM900. There is an Espressif ESP32 communicating with SIM5300E. All communication is OK.

I need to transmit messages to my server using UDP protocol.

The AT sequence I am using follows:

AT+CFUN=4
ATZ
AT+CIPSHUT
AT+CIPMUX=0
AT+CIPMODE=0
AT+CFUN=1
AT+CREG?  --> loop until arrives 0,1
AT+CGATT=1
AT+CSTT="myprovider.com"
AT+CIICR
AT+CLPORT="UDP",1100
AT+CIPSRIP=1
AT_CIPHEAD=1
AT+CIFSR
AT+CIPSTART="UDP","myserver",1100  --> wait until arrives "CONNECT OK"

to transmit:

AT+CIPSEND
--> wait for ">"
--> message + 0x1A ( ctrl Z )
--> "SEND OK"

The problem is that nothing arrives at my server in first instance.

I can try several UDP transmissions, all returns "SEND OK", but nothing arrives at server.

But, if I transmit anything from server, manually using the SIM5300E IP (obtained from AT+CIFSR), the message arrives at SIM5300E and, after that, I can send/receive normally at SIM5300E.

The problem is that my server doesn't know the SIM5300E IP at first time, as this IP is dynamically obtained from GSM service. Only when it receives the first message it will know. So, my server can't send the first message to unlock this issue.

Can somebody give me some ideas on how to fix this UDP transmission issue, please?

Thanks in advance.

Sergio

 

[serkam]

Hi
I already solved this issue.
The problem was in my NAT table in internet router. I simply forgot to translate the port 1100 to route to correct IP of the server running inside my local network.
Doing this, all worked fine.
In other words, the AT sequence that I posted previously is working fine.
Thank you for your attention.
Sergio