There is lots of confusion between Application program interface and Short Message Peer-to- Peer,which is the best tool for sending sms,both are the dominate option for developer that are looking to settle on a quality and High performance for SMS Application.
Today, a web-based application is not enough to reach your customers. People are very smart, they are using iphone, mobile, tablets etc. devices in its daily life. These devices also have a lot of apps for making the life easy. Actually, we are moving from the web towards apps world.
So, if you like to expose your service data to the browsers and as well as all these modern devices apps in fast and simple way, you should have an API which is compatible with browsers and all these devices.
SMPP solution is better suited to corporate brands with high volume bulk SMS requirements. SMPP is a TCP/IP based protocol that is more commonly used when connecting to mobile operators and service providers. The primary benefit of this protocol over a plain GSM modem is speed and overall capacity.
There is not really a hardware requirement. There is a service provider requirement, as you need to be connecting to an SMS service provider using the SMPP protocol.
Messages sent over SMPP are routed directly to and from the wireless service provider over a secure private network. Most major wireless service providers can provide confirmation of message delivery.
The greatest benefit to SMPP is the fact that messages are two-way, enabling mobile phone subscribers to respond to the messages you send them. SMPP also supports the ability to schedule the message delivery date and time among other functions.