have developed an SMS gateway using VB, mscomm and Wavecom GSM modems, that receives requests for data via SMS and sends a reply to requestor via SMS.
however, now that my user loads have increased, i am experiencing high traffic at peak hours. this causes outgoing sms to collide with a half-incoming SMS. (fully received SMSes on the sim are cleared before attempting to send outgoing)
how do i detect if the signal is busy and it is safe to send an SMS out, and if a collision should occur, how do i trap it, and at what event/time period should i wait before attempting to resend (is there a command that says "resend last sms"?)
to reproduce problem, try firing up to 10 sms from a mobile to a gsm modem that is set to send a reply. most sms applications developed locally have not encountered the problem due to insufficient traffic congestion.
i am now a slave to the server, as i have to monitor the gateway everyday (on public holidays too!) and restart the application after it hangs. please help.
500 points to anyone who has a solution. if you can solve my problems once and for all with source code example. then i'm willing to give 3582 pts (all i've got)