You can install a network monitoring tool like Wireshark and then take a look at the packets being sent and received.
In the screenshot below:
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Filtered by the sending server IP address.
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Look at the instance that has larger length (filesize).
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Click on the HL7 content which will highlight the packet.
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The example shows the footer of "0d 1c" but we default to "1C 0D"
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The header is up higher in the message and will be at the begining of the highlighted text.