When an smpp client establishes a connection using SMPP, can be done in three modes:
The client can only receive messages or delivery reports from the SMSC.
Connection is not allowed to transmit messages over the connection, it can only receive messages. Any attempt to submit messages over this connection will result in the error
ESME_RINVBNDSTS (Incorrect BIND Status for given command).
The client can only submit messages to the SMSC.
Connection is allowed to transmit messages only over the connection, it cannot receive any messages.
The client can both send and receive messages to and from the SMSC.