SMS messaging server software sends SMS and text messages to: pagers, mobile phones, PIMs, wireless devices. Messages can be accepted from: networked computers, email, web pages (CGI), commandline executables, text files, serial ports, modems. Messages can be delivered via: the Internet (SNPP, WCTP, SMTP), modems (TAP, UCP, GSM, TONE), direct serial connections (TAP). Advanced features: redundant outbound connections, message rerouting on failure.

SMS Gateway is a highly efficient middleware system fetching information from transaction systems or large databases and sending them in text or binary form using SMS as a bearer to any GSM or CDMA cellular network .
SMS Gateway Providers

SMS gateway providers can be divided into 2 categories in terms of how they require you to pay for their SMS service:

Credit-based
You purchase a number of credits from the SMS gateway provider. Sending one SMS message will cost you one or more credits, depending on the country you send the SMS message to. For example, sending an SMS text message to India might cost you one credit while sending an SMS text message to the United States might cost you two credits.

SMS-based
You purchase a number of SMS messages from the SMS gateway provider. The cost for sending one SMS message is the same for all destinations. For example, if you purchase ten SMS messages, you can send at most ten SMS messages no matter the destination is India or the United States.

SMS API

SMS APIs which deliver a quick, seamless, turn-key approach to developing SMS solutions. With COM, dotNET, Java and PHP, our SMS SDK ensures a solution is available for nearly any platform or operating system.

SMS API Functionalities are Sending, Receiving and Delivery Reports