Message and Communications Protocol
A message using the Elavon Gateway API format consists of a list of fields, each assigned a field number. The field number (which can be 0-filled to 4 characters or just the number up to 4 characters) is followed by a comma, which is followed by the field value. Each line is terminated with a <CR><LF>. Alternatively, each line might be terminated by a UNIX <LF>. The message is terminated with an <EOT>. See below for sample messages.
The communications protocol between the POS process and Simplify is TCP/IP or RS-232 (Serial).
Control Characters include:
(0x02) = <STX> 1 byte, hex 2
(0x0D) = <CR> 1 byte, hex D
(0x0A) = <LF> 1 byte, hex A
(0x04) = <EOT> 1 byte, hex 4
(0x03) = <ETX> 1 byte, hex 3
(0x??) = <LRC> - Computed
Simplify will act as the TCP/IP Server. The POS process will act as the TCP/IP Client. The POS process will initiate the connection to Simplify.
Simplify-POS messaging can use plain TCP/IP or TCP/IP with TLS 1.2.
If multiple POS workstations are associated with a single PIN Pad, Simplify assumes that the POS process ensures that there is only one outstanding transaction per PIN Pad.
Simplify RS-232 (Serial)
Appendix B describes the Simplify RS-232 communication protocol.
Simplify RS-232 communication could optionally be over USB emulating RS-232.
Note: Sample messages shown in the remainder of this document do not show the control characters.