# Racket UPnP module

This directory contains a small, layered UPnP control-point implementation.
The public interfaces deliberately hide SSDP, XML, SCPD and SOAP details unless
the generic service escape hatch is used.

## Module layout

```text
upnp/main.rkt                         generic public interface
upnp/didl-lite.rkt                    DIDL-Lite metadata generation
upnp/media-renderer.rkt               high-level renderer operations
upnp/media-server.rkt                 high-level MediaServer browser
upnp/services/av-transport.rkt        playback transport
upnp/services/rendering-control.rkt   volume and mute
upnp/services/connection-manager.rkt  protocol and connection information
upnp/services/content-directory.rkt   media-server browse and search
upnp/ssdp.rkt                         low-level SSDP discovery
upnp/device.rkt                       device-description parsing
upnp/service.rkt                      SCPD inspection and SOAP calls
```

The collection can be required as `upnp` when the package root is on Racket's
collection path.

## Generic device discovery

```racket
#lang racket/base

(require upnp)

(define devices
  (query-upnp-devices '(media-renderer scanner)
                      #:interface "10.7.3.118"
                      #:dns? #t))

(for ([device (in-list devices)])
  (printf "~a: ~a\n"
          (upnp-device-kind device)
          (upnp-device-name device)))
```

Known friendly device kinds are returned by:

```racket
(upnp-device-kinds)
```

Without a kind, all described UPnP devices are returned:

```racket
(query-upnp-devices)
```

Unknown vendor-specific device types are retained and classified as
`'unknown`; their original URN remains available through `upnp-device-type`.

## Service inspection

```racket
(define renderer (car (query-upnp-devices 'media-renderer)))

(for ([service (in-list (upnp-device-services renderer))])
  (printf "~a: ~a\n"
          (upnp-service-kind service)
          (upnp-service-actions service)))
```

`upnp-service-call` is the generic escape hatch for standard services that do
not yet have a typed module and for manufacturer-specific services.

## One module per known service

```racket
(require upnp/services/av-transport
         upnp/services/rendering-control)

(define transport (device-av-transport renderer))
(define rendering (device-rendering-control renderer))

(av-transport-set-uri!
 transport
 "http://10.7.3.118:8080/media/test.flac")
(av-transport-play! transport)
(rendering-control-set-volume! rendering 30)
```

The currently implemented typed service modules are:

- `upnp/services/av-transport`
- `upnp/services/rendering-control`
- `upnp/services/connection-manager`
- `upnp/services/content-directory`

A typed service value is still the generic `upnp-service` value. No extra
wrapper objects or public constructors are needed.


## Media-server browser

The higher media-server layer parses ContentDirectory DIDL-Lite into ordinary
containers, items and resources:

```racket
(require upnp/media-server)

(define synology
  (car (query-media-servers #:interface "10.7.3.118")))

(define root (media-server-root synology))
(define music
  (findf (lambda (entry)
           (and (media-container? entry)
                (string=? (media-entry-title entry) "Muziek")))
         root))

(define entries (media-container-children synology music))

(for ([entry (in-list entries)])
  (printf "~a: ~a\n"
          (if (media-container? entry) 'container 'item)
          (media-entry-title entry)))
```

A media item can advertise several resources.  Their URLs are available with
`media-item-resources` and `media-resource-uri`.  Containers are followed one
level at a time; the published hierarchy can be a logical artist/album/genre
view rather than the physical filesystem.

## Media-renderer convenience layer

Normal playback code need not mention AVTransport or SOAP:

```racket
(require upnp
         upnp/media-renderer)

(define files
  (start-media-file-server
   "http://10.7.3.118:8080/media/"
   #:listen-ip "10.7.3.118"))

(define uri
  (media-file-server-publish!
   files
   "C:/muziek/test.flac"
   "test.flac"))

(define denon
  (car (query-media-renderers
        #:interface "10.7.3.118"
        #:dns? #t)))

(media-renderer-play-uri!
 denon
 uri
 #:metadata
 (media-file-server-didl-lite
  files
  uri
  #:title "Test track"
  #:duration 639))

(media-renderer-seek! denon 120)
(media-renderer-set-volume! denon 30)
```

`query-media-renderers` returns all UPnP MediaRenderers by default. Add
`#:dlna-only? #t` to retain only devices advertising `X_DLNADOC`.

For local files, `media-file-server-publish!` supplies a byte-range-capable
HTTP URL. `media-file-server-didl-lite` generates matching DIDL-Lite metadata,
including MIME type, file size, duration, and `DLNA.ORG_OP=01`. Some renderers,
including certain Denon models, only advertise `Seek` after receiving this
metadata. Generate and pass matching metadata for both the current URI and a
preloaded next URI.

## Documentation and tests

The Scribble manual is in `upnp/scribblings/upnp.scrbl`.

The test file `upnp/tests/upnp-test.rkt` uses a local mock HTTP/SOAP server and
covers service discovery from SCPD, SOAP calls, SOAP faults, AVTransport,
RenderingControl, ConnectionManager, ContentDirectory and DIDL-Lite media
server browsing.