Short Message Peer-to-Peer ProtocolCommunications protocol that is standardized within the WAP Forum as the protocol for applications to communicate with SMSCs. This is an additional module for MDS 2.5 for support of the SMPP Short Message Service Centre and ESME's (External Short Message Entities). The protocol requires a connection dedicated to either incoming or outgoing messages. Therefore, two connections are required in order to both send and receive messages using SMPP. By design, the Fenestrae Mobile Data Server assigns only a single communication module to a service. Therefore, two services are required for a bi-directional connection.