Hl7 Standard 1
An important part of the HL7 standard is the ACKnowledgment protocol.
Every time an application accepts a message and consumes the message data, it is expected to send an ACKnowledgment message back to the sending application.
The sending application is expected to keep on sending a message until it has received an ACK message.
If you do not follow this rule, data may be lost in transmission.