Has anyone tried to solve a similar problem of connecting two programmes? In Virtools there is a so called building block that allows to send web messages via the post method - to send a new message the connection has to be closed, but the problem was that [netreceive] couldn't do this.
for HTTP 1.1, the easiest thing would probaly be making a [httpd] object in gridflow (encapsulating Mongrel or Webrick). there might also be a httpd implemented as a PD library for one of the two PD-as-browser-plugin things, but im not exactly sure.. google for IARS/UPF/IEM etc...
generally interapp communication with PD has been netsend and OSC however..