Editing EMI (protocol) (section)

==Syntax==

A typical EMI/UCP exchange looks like this :

  ^B01/00045/O/30/66677789///1//////68656C6C6F/CE^C
  ^B01/00041/R/30/A//66677789:180594141236/F3^C

The start of the [[Packet (information technology)|packet]] is signaled by ^B (STX, hex 02) and the end with ^C (ETX, hex 03).  Fields within the packet are separated by / characters.

The first four fields form the mandatory header.   the third is the ''operation type'' (O for operation, R for result), and the fourth is the ''operation'' (here 30, "short message transfer").

The subsequent fields are dependent on the operation.  In the first line above, '66677789' is the recipient's address ([[telephone number]]) and '68656C6C6F' is the content of the message, in this case the [[ASCII]] string "hello".  The second line is the response with a matching transaction reference number, where 'A' indicates that the message was successfully acknowledged by the SMSC, and a timestamp is suffixed to the phone number to show time of delivery.

The final field is the [[checksum]], calculated simply by summing all bytes in the packet (including slashes) and taking the 8 [[least significant bit]]s from the result.

The full specification is available on the LogicaCMG website developers' forum, but registration is required.