This is a very simple method to Send Sms via GSM Modem so without much explanations let's get into it. Thing's you'll need : GSM Modem with a SIM Libraries :GSMCommServer.dllGSMCommShared.dllGSMCommunication.dllPDUConverter.dll If you've installed the Modem software you'll be able find all the libraries needed. Just go to add Reference and add the mentioned libraries (without them this