doc/OONI/Backend/HTTPServer.md

+The backend HTTP server is used to assist in running tests that related to HTTP censorship. 
+
+At the momento two main kinds of services are offered by the backend
+
+  * An HTTP server that replies with random data of selectable length that can contain a certain keyword
+  * An HTTP server that replies in json format the headers that have been sent by the client.
+
+The implementation of this can be found here: https://gitweb.torproject.org/ooni-probe.git/blob/HEAD:/oonib/testhelpers/httph.py
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