My HTTP 200 OK response has no line based text data, says Expert Info (Note/Malformed): HTTP body subdissector failed, trying heuristic subdissector

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I checked a couple of the responses that have no "line based text data" and all of them have no content:

POST /startSelfTest/Disk%20Storage/1/service HTTP/1.1
Host: 192.168.86.44:8080
Connection: keep-alive
Content-Length: 0
Accept: */*
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36
X-Requested-With: XMLHttpRequest
Origin: http://192.168.86.44:8080
Referer: http://192.168.86.44:8080/selfTest
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Date: Thu, 10 Sep 2020 00:34:35 GMT
Content-Type: text/html; charset=utf-8
Server: TwistedWeb/16.0.0

0

The Transfer-Encoding: chunked header means that content is generated on the fly and that a Content-Length header can't be generated up front. In a chunked response, the response data can consist of multiple chunks. Each chunk will have a header line indicating how much data the chunk has and then the chunk of data. The last "chunk" will have length 0 to indicate that the object is now complete.

In the responses you are looking at, there is only one chunk header with the value 0, indicating there is no data coming from the server. That's why wireshark does not show any "line based text data", there is none to show.