logging added.

scribblings/main.scrbl

@@ -16,15 +16,23 @@ interface.
 @defproc[(query-upnp-devices
           [kinds (or/c 'all symbol? (listof symbol?)) 'all]
           [#:interface interface (or/c #f string?) #f]
-          [#:dns? dns? boolean? #f])
+          [#:dns? dns? boolean? #f]
+          [#:mx mx (integer-in 1 5) 3]
+          [#:timeout timeout (or/c #f positive-real?) #f]
+          [#:repeat repeat exact-positive-integer? 3])
          (listof upnp-device?)]{
 Discovers and describes matching UPnP devices.
 
 @racket['all] returns all described devices. A symbol such as
 @racket['media-renderer] selects one known kind, and a list selects several
 kinds. When @racket[interface] is a local IPv4 address, SSDP multicast is sent
-through that interface. Reverse DNS lookup is only attempted when
-@racket[dns?] is true.
+through that interface. Reverse DNS lookup is only attempted when @racket[dns?] is true.
+
+@racket[mx] is the SSDP response delay advertised in the M-SEARCH request.
+The default receive window is @racket[mx] plus one second. An explicit
+@racket[timeout] overrides that receive window and must be at least
+@racket[mx]. @racket[repeat] controls how many M-SEARCH requests are sent;
+the requests are spaced 250 milliseconds apart.
 }
 
 @defproc[(upnp-device-kinds) (listof (cons/c symbol? string?))]{