API for Zeroconf connection to other devices on the network

[pezzy-o]

Problem:
Spotify Web API only allows me to connect to devices which are specifically registered to my account, rather than those devices which advertise themselves over mdns on my local network.

Possible solution:
I'd like to be able to use an API in order to programmatically connect to any Spotify devices on my local network, using Zeroconf. I can see that you've done the hard yards to be able to connect the librespot-java player via Zeroconf: would it be possible to onboard other players using a similar method, and incorporate this into the API?

Background / use case:
I have created an application in Spotify, and I can use it for Spotify Web API calls, including connecting to those devices which are registered to my Spotify account. I use Sonos speakers, which seem to rely more on Zeroconf connections for devices on the local network, so when I use the Spotify Web API to list available devices using the Spotify Web API, unless I've recently connected to the Sonos device specifically through the Spotify app, the Sonos devices do not appear in the list of available devices. The Sonos devices still show up on the Spotify Connect app (they're still advertised and over mdns), just not in the Web API, presumably because they aren't registered specifically to my account, and need to be available to other users on my local network.

[devgianlu]

So you'd like an API endpoint to list devides available on your network and one to connect to them?

[pezzy-o]

Basically yes - that was just a long-winded way of asking, so I could explain the use case.

[devgianlu]

First part should be relatively easy: just need to make a mDNS probe and get the results. For the second one we need to craft the zeroconf blob which ultimately is a lot of wrapping around stored credentials data.

I'll start by modifying zeroconf-java to allow probing.

[pezzy-o]

Awesome - thanks for getting started so quickly! This might be me, but I'm getting an authorisation failure (401) when I try to compile (mvn clean package):
Downloading from github: https://maven.pkg.github.com/devgianlu/*/xyz/gianlu/zeroconf/zeroconf/1.2.1/zeroconf-1.2.1.pom
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for librespot-java 1.5.6-SNAPSHOT:
[INFO]
[INFO] librespot-java ..................................... SUCCESS [ 0.150 s]
[INFO] librespot-java sink API ............................ SUCCESS [ 2.256 s]
[INFO] librespot-java default sink ........................ SUCCESS [ 0.584 s]
[INFO] librespot-java decoder API ......................... SUCCESS [ 0.385 s]
[INFO] librespot-java lib ................................. FAILURE [ 1.125 s]
[INFO] librespot-java DACP interface ...................... SKIPPED
[INFO] librespot-java player .............................. SKIPPED
[INFO] librespot-java api ................................. SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.275 s
[INFO] Finished at: 2021-05-08T20:10:59+10:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project librespot-lib: Could not resolve dependencies for project xyz.gianlu.librespot:librespot-lib:jar:1.5.6-SNAPSHOT: Failed to collect dependencies at xyz.gianlu.zeroconf:zeroconf:jar:1.2.1: Failed to read artifact descriptor for xyz.gianlu.zeroconf:zeroconf:jar:1.2.1: Could not transfer artifact xyz.gianlu.zeroconf:zeroconf:pom:1.2.1 from/to github (https://maven.pkg.github.com/devgianlu/*): Authentication failed for https://maven.pkg.github.com/devgianlu/*/xyz/gianlu/zeroconf/zeroconf/1.2.1/zeroconf-1.2.1.pom 401 Unauthorized -> [Help 1]

[devgianlu]

Yep, I know. The CI is also failing, there's something wrong with the CI on zeroconf-java because I had to switch away from Travis and it broke. Hadn't time to fix it yet.

As a workaround you can either clone zeroconf-java and do mvn clean install or download the JAR and install it manually.

[pezzy-o]

mvn clean install is giving me the same result. I'm not sure how I would modify the compiled JAR file: I took a look inside the archive and couldn't immediately find the same filenames as were modified in the commit, but I'm not overly familiar with java, maven etc. so might be best for me to just wait until the CI is fixed and I can compile it again. Thanks @devgianlu

[devgianlu]

@benturnberg You should be good now.

[pezzy-o]

Great - I can compile again 🤘

Using the librespot-api-1.6.1-SNAPSHOT.jar, I get the following result when running a POST to http://localhost:24879/discovery/list:

2021-05-10 16:26:25,521 TRACE selector:564 - Selected on sun.nio.ch.WindowsSelectorImpl@4166658f
2021-05-10 16:26:25,521 TRACE selector:583 - Selected key channel=java.nio.channels.SocketChannel[connected local=/[0:0:0:0:0:0:0:1]:24879 remote=/[0:0:0:0:0:0:0:1]:59437], selector=sun.nio.ch.WindowsSelectorImpl@4166658f, interestOps=1, readyOps=1 for java.nio.channels.SocketChannel[connected local=/[0:0:0:0:0:0:0:1]:24879 remote=/[0:0:0:0:0:0:0:1]:59437]
2021-05-10 16:26:25,521 TRACE selector:169 - Calling handleReady key 1 for java.nio.channels.SocketChannel[connected local=/[0:0:0:0:0:0:0:1]:24879 remote=/[0:0:0:0:0:0:0:1]:59437]
2021-05-10 16:26:25,522 TRACE listener:91 - Invoking listener io.undertow.server.protocol.http.HttpReadListener@22e2f427 on channel org.xnio.conduits.ConduitStreamSourceChannel@f641445
2021-05-10 16:26:25,522 TRACE transfer-encoding:119 - No content, starting next request
2021-05-10 16:26:25,522 TRACE selector:539 - Beginning select on sun.nio.ch.WindowsSelectorImpl@4166658f (with timeout)
2021-05-10 16:26:25,522 TRACE nio:550 - Select, queue is empty
2021-05-10 16:26:26,274 TRACE selector:564 - Selected on sun.nio.ch.WindowsSelectorImpl@4166658f
2021-05-10 16:26:26,275 TRACE selector:539 - Beginning select on sun.nio.ch.WindowsSelectorImpl@4166658f (with timeout)
2021-05-10 16:26:26,275 TRACE nio:550 - Select, queue is empty
2021-05-10 16:26:26,274 TRACE HttpServerExchange:1866 - Starting to write response for HttpServerExchange{ POST /discovery/list}
2021-05-10 16:26:26,277 TRACE safe-close:151 - Closing resource io.undertow.server.HttpServerExchange$DefaultBlockingHttpExchange@6da75879
2021-05-10 16:26:26,277 TRACE safe-close:151 - Closing resource io.undertow.server.HttpServerExchange$DefaultBlockingHttpExchange@6da75879
2021-05-10 16:26:27,002 TRACE selector:564 - Selected on sun.nio.ch.WindowsSelectorImpl@4166658f
2021-05-10 16:26:27,002 TRACE nio:611 - Running task io.undertow.util.DateUtils$2@4c001e57
2021-05-10 16:26:27,002 TRACE selector:539 - Beginning select on sun.nio.ch.WindowsSelectorImpl@4166658f (with timeout)
2021-05-10 16:26:27,002 TRACE nio:550 - Select, queue is empty
2021-05-10 16:26:30,906 TRACE selector:564 - Selected on sun.nio.ch.WindowsSelectorImpl@4166658f
2021-05-10 16:26:30,906 TRACE nio:611 - Running task io.undertow.server.protocol.ParseTimeoutUpdater@6b5bf646
2021-05-10 16:26:30,907 TRACE selector:539 - Beginning select on sun.nio.ch.WindowsSelectorImpl@4166658f (with timeout)
2021-05-10 16:26:30,907 TRACE nio:550 - Select, queue is empty

[devgianlu]

You should get the list of devices in the response body.

[pezzy-o]

Sorry, should have included that - the response body is:

{
    "value":  [

              ],
    "Count":  0
}

[pezzy-o]

Just to add to this, the API does work for me when invoking /player/next for example... On the other hand, it also returns a blank response when (while connected) I invoke /web-api/v1/me/player/devices.

[devgianlu]

I think the problem goes back to zeroconf-java not being able to discover your librespot-java client.

[pezzy-o]

Anything I can check on my side? I tried disabling AV and firewall just as a sense-check, still the same though.