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.
Control Characters are defined as follows:
<CR> = (0x0D) 1 byte, hex D
<LF> = (0x0A) 1 byte, hex A
EOT = (0x04) 1 byte, hex 4
Note: Sample messages shown in this document do not show the control characters.
The communications protocol between the POS process and Simplify is TCP/IP or RS-232 (Serial).
TCP/IP communications between the POS and Simplify is by wired ethernet.
Simplify will act as the TCP/IP server. The POS process will act as a TCP/IP client and initiate the connection to Simplify.
Simplify-POS messaging can use plain TCP/IP or TCP/IP with TLS 1.2. Depending on security configuration, a certificate may be needed if TLS is used.
Appendix B describes the Simplify RS-232 communication protocol.
Simplify RS-232 communication could optionally be over USB emulating RS-232.