Hi, is it possible to start/stop handlers for individual modems in a config with multiple modems so I do not need to restart the server with modified config?

No, it's not possible. This is because smsd main process reads and checks the configuration and then forks itself and all modem processes.

However, restarting the smsd does not take very much time and it's safe when using init.d/sms3 script. No messages are lost even with heavy traffic, because this script waits until all modems have done their job.

Thank you, my problem is not about the time needed for restart - just we have monitoring setup on the smsd log file and every shutdown generates an alert in the ticketing system and I need to avoid that when only some of the forked modem processes get stuck and I have to somehow restart it ...

petmar wrote

some of the forked modem processes get stuck and I have to somehow restart it ...

What do you mean with this? Your modem was freezed and you had to disconnect it and after plugged it in again it got different device name? In this case udev might help. Also you can try a modem setting keep_open = no which may help with unstable devices.

Well, at the moment I don't know what's going on there. I'm on a Win/Cygwin setup with usb modems. After some time sms server stops communicating with modems (one after another) until only one of them is online - this is randomly. There is no error reported in the logs even with the highest loglevel - the modem just stops responding:

2009-06-15 13:51:06,6, LOGIGSM1: Checking device for incoming SMS
2009-06-15 13:51:06,6, LOGIGSM1: Checking if modem is ready
2009-06-15 13:51:06,7, LOGIGSM1: -> AT

and after that nothing ...

I'm suspecting that there might be a problem with power supply of the modems - if there is only one pluged in the system works great, no problems, no errors, ... When I start adding modems the problems start to appear. I have shipped a new externally powered USB hub with higher rates on output voltage on the adapter to that location, hopefuly it will solve the issue.

EDIT:
I forgot - sometimes there is following line recorded before what's mentioned above:
2009-06-15 13:50:56,6, LOGIGSM1: No SMS received (reading interrupted)

No SMS received (reading interrupted) means that there was a message but reading got incorrect answer or timeout.

When checking if modem is ready, after AT command there should be more log messages. In this case it looks like USB driver is freezing and smsd cant do nothing as the driver does not return.

Typically one USB modem takes current about 150 mA (peak) which is not very much, but with many devices and weak interface problems may occur.

You're right, either a driver problem or that power supply on the usb hub. Hopefully the modem driver guys will respond soon.
Thanks for your time.