java.nio.BufferUnderflowException when trying to set Bluetooth SPP profile

Hi!

This code gets the buffer underflow exception.

(defn start-fake-hardware []
  (let [client (dbus/init-client! (dbus/system-sock)
                                  (fn [v]
                                    (println "DBus Reply: " v)))
        result (dbus/write-message
                 client
                 {:type    :method-call
                  :headers {:path "/org/bluez"
                            :member "RegisterProfile"
                            :interface "org.bluez.ProfileManager1"
                            :destination "org.bluez"
                            :signature "osa{sv}"}
                  :body    ["/org/bluez/spp"                       ; Profile path
                            "00001101-0000-1000-8000-00805f9b34fb" ; SPP UUID
                            {"Name"    "Serial Port"
                             "Channel" 1}]})]
    (prn @result)))

One thing to note is that the "Channel" value that is sent should be a variant containing a uint16, and it seems like the code will encode it wrong. I don't know if that's the problem.

Start with the supplied start-fake-hardware example and trace dbus/write-message while comparing the osa{sv} signature with the body, especially the Channel value. Verify how variants and uint16 values are encoded; done means the message no longer raises BufferUnderflowException and the Bluetooth SPP profile registration succeeds.