The following screenshot explains the settings available for the HL7 Listener Utility:

The Parse delimiter characters from MSH segment checkbox is referring to the HL7 protocol which allows the redefinition of the delimiter characters in the MSH segment. Normally this should just be left checked. However, it can be useful if incoming messages have incorrectly formatted MSH segments.

Each incoming message is "ACKnowledged" by the HL7 listener and logged into the specified message log file. Each message is formatted in a single line with 0x0D characters separating the segments and a line feed at the end of each message. In an editor like notepad when word wrap is off, it appears like each message is one line in the file.

The log file cannot be shared by two running instances of the HL7 Simulator and Listener. If this is required, a different log file should be specified for each application.

The log file can then be used in the HL7 Simulator to replay the flow of messages. The HL7 Simulator is very specific about the input message log file format. As a result it will only accept the format generated by the HL7 Listener.