The SMPP protocol is an open, telecommunications industry standard protocol designed to provide a flexible data communications interface for transfer of short message data between any kind of Message Center (e.g. Short Message Service Center – SMSC, GSM Unstructured Supplementary Services Data – USDD, etc.) a PC-based SMS application system (e.g. Ozeki NG SMS Gateway software). This way, SMPP protocol can be used to allow third parties to submit short text messages, even bulk messages. SMPP protocol enables short message entities (SMEs) outside the mobile network to connect to the SMSC. Those non-mobile message software (such as Ozeki NG SMS Gateway) that send messages to or receive them from the SMSC are called External Short Message Entities (ESMEs). The protocol is based on the exchange of request/response PDUs (Protocol Data Units or packets) between the ESME and the SMSC over an underlying TCP/IP or X.25 network connection. The exchange of SMS messages between an ESME and SMSC via SMPP may be categorized under three distinct groups of transactions as follows: Messages sent from the ESME (Transmitter) to the SMSC Messages sent from the SMSC to the ESME (Receiver) Messages sent from the ESME (Transceiver) to the SMSC and messages sent from the SMSC to the ESME (Transceiver). The most commonly used versions of SMPP are v3.3 (this is the most widespread standard) and v3.4 (that adds transceiver support). In order to exemplify how can be used SMPP protocol in business life, let’s look at Ozeki Android SMPP SMS Gateway that uses this protocol. This is a mobile application that enables automated SMS messaging from the corporate IT system through a smartphone. You need a PC-based messaging software (e.g. Ozeki NG SMS Gateway that compatible with Windows operation system) and an Android smartphone (e.g. Samsung, LG, Sony Ericsson, HTC, etc.). First of all, you need to install the application on your phone. After the installation, you need to connect your phone to the PC. Your SMS software can establish connection with Ozeki Android SMPP SMS Gateway using SMPP 3.4 protocol and the application can accept connections from your SMS software through WIFI or over the Internet. Since this application and the conventional GSM modems also use SMPP protocol, this application can replace these modems. After you have installed SMPP connection in your messaging software you need to specify some data given by your Ozeki Android SMS Gateway. This way your smartphone can be used as an SMPP SMS Gateway.