Message Verification

Message verification begins with reading the message from the external system. The message is expected to match the MLLP envelope, since both HLLP and MLLP envelopes have the Start of Block (SOB), End of Data (EOD), and a Carriage Return (CR) in common.

If a message fails the read verification, it is considered bad data. If read by an inbound Adapter, this failure causes the Adapter to generate a Canned HL7 NAK. An outbound Adapter ignores the message and logs a warning, reporting the nature of the problem to the log file.

An HLLP envelope needs further verification as to whether it is data or a NAK, as well as the Block Checksum and Block Size. The Adapter behaves as described above if the HLLP envelope verification fails.

After stripping the message envelope, the RA hands the de-enveloped message to the inbound Collaboration where it is parsed into the generic event Message Library. This ensures that the general form and MSH segment are valid. If the MSH property is set, the Collaboration verifies that the fields specified in the HL7 segment section are the same as those of the received MSH, otherwise, a NAK is returned.