SMS send error from C# application using GSM modem

0
votes

I develop a C# application that has (text mode) SMS communication capabilities. Usually it works fine, but sometimes SMS sending goes wrong. Here is what SOMETIMES happens:

AT+CMGS="+3630xxxxxxx"

> text CTRL+Z

Normally it should answer this: +CMGS: SMS ID\r\n OK\r\n

Sometimes, it does not answer anything after sending CTRL+Z even after 30 seconds, the CMGS: answer does not come from the modem, sometimes the answer is the SMS text itself. After I try to send another SMS, it answers +CMS Error: 515. It means, that modem is busy. I think it is busy because there is an SMS in the outbox. Note, that other AT commands still work perfectly.

So, what to do in this situation? ...when +CMGS: SMS ID\r\n OK\r\n does not come when sending SMS?

I use .net framework2 and its serial communication features. Modem is a Simcom 300 d.

Pls. help me, thanks in advance!

1
c#windowssmsmodemgsm

1 Answers

0
votes

Send byte ctrlZ = 26; for terminating the SMS.

i.e. [ 026 ( 00011010 ) 0x1A ] [ ] byte after you are done with text. [ decimal (binary) hex ] [ascii representation] . The ascii can't be seen here.