ErrInvalidPDU indicates invalid pdu payload.

ErrShortMessageLengthTooLarge indicates short message length is too large.

ErrUDHTooLong UDH-L is larger than total length of short message data.

ErrUnknownCommandID indicates unknown command id.

ErrWrongDateFormat indicates wrong date format.

SmppErr indicates smpp error(s), compatible with OpenSMPP.