Hi guys, I have a modem connected to my machine. Both My C# code and Hyperterminal can open the COM port, but when the command AT is sent, no reply is got. In control panel->Modems->Query modem however, the modem responds!!! Anybody who has ever experienced this?

possibly the line feed isnt being sent correctly

Thanks LizR for the quick response. The thing is, at times, it works just fine. Hyperterminal gets a response and so does my code. But the modem reaches a point and 'decides' to respond to the Query modem utility only. Not even other applications that work in the same manner are able to get a response!!

Then it sounds like you have a port conflict

I looked up hardware conflicts and how to resolve them. In device manager, you select view, show hidden devices, then uninstall invalid devices. The com ports associated to the devices are released and can be used by subsequent hardware. I think the cause of this problem is that hardware is unplugged without uninstalling, making it's associated port still reserved by the system. Now my modem is up and alive. Thanks LizR.