i am developing attendance software with sms support current i have tried sending sms with one gsm modem , but the it took 1.5 hour to send 3500 sms , so i wan to use 4 gsm modems having separate com ports , now the problem is i am unable to design the alogrith to distribute the employees mobile numbers to distrinute over 4 gsm modems , kindly help me in idea how to do it , or any alogrithm suggestion, i will be very thank full to all of you .

Small world. In a time not long ago I had to update firmware over serial ports so the design was in 2 parts.

  1. A master app to spawn the update app and issue commands to the update apps.
  2. The update app would get it's instructions on the update, make the connection and perform the update and then respond or send the done message back to the master app.

Since I had over a dozen serial ports this proved to leverage the most from the cores in the PC. You will find that a single thread in C# doesn't tap all the power (of the dark side.)

I'd re-use my old idea if I had your system to design.