A bind, in the specific case of connecting to Sinch via SMPP, is a single connection using the SMPP protocol. There are three ways to open a connection using SMPP: Transmitter – send short messages to the SMSC and receive responses from SMSC Receiver – receive delivery receipts from the SMSC and return the corresponding responses Transceiver – send and receive messages to and from the SMSC over a single SMPP session.