An interesting idea from being Mac developers, the motto was always put a refcon field in your records. It was how you extended handles, and making it a number, not a handle showed you were klooging and knew it. I think it should be a string. A string, the body of the request. GET requests have empty bodies.
POST requests do, as do PUTs.
Further, if the header contains a Cookie header, it's parsed into a sub-table of requestHeaders, called cookies. The responder is expected to set the value of this field. A GET request, for example, would yield a response body containing the HTML for the page being requested. A table, the header values you want to be included in the response. A number, it identifies the TCP-IP stream for this request.