The message type is passed in the type parameter.
TYPE_UNKNOWN = -1
// PIN Pad information
TYPE_INFO = 2
// payment
TYPE_PAYMENT = 10
// payment response: non-card tender type selected by customer
TYPE_PAYMENT_TENDER = 11
// payment state (transient message)
TYPE_PAYMENT_STATE = 12
// void for a previous payment
TYPE_TX_VOID = 20
// refund for a previous payment
TYPE_TX_REFUND = 21
// capture of a previous Auth transaction
TYPE_TX_CAPTURE = 22
// tip adjustment for a previous Auth transaction
TYPE_TX_TIP_ADJUSTMENT = 23
// current open batch report
TYPE_REPORT_BATCH = 50
// current open batch total
TYPE_REPORT_BATCH_TOTAL = 51
// Cash Discount report
TYPE_REPORT_CASHDISCOUNT = 55
// closing the current batch
TYPE_BATCH_CLOSE = 80