CLI Application freezes when trying to connect

[Timboooh]

Description

I'm using the example command listed in the usage section of the README.
Librespot starts up as usual and is detected properly in the Spotify Desktop Client.
When I try to connect the librespot application freezes, and can't be terminated using the CTRL+C shortcut.
I've tried it on my home network and also on LTE using an Android Hotspot.

Version

$ librespot --version
'librespot 0.6.0 VERGEN_IDEMPOTENT_OUTPUT (Built on 2025-01-24, Build ID: jn3b7UuP, Profile: release)

How to reproduce

1. Launch librespot --verbose --name librespot
2. Connect using Spotify Desktop Client
3. Spotify Desktop gets stuck on 'Connecting to librespot' and fails after a while
4. Librespot freezes

Log

librespot --verbose --name librespot
[2025-01-24T16:07:44Z INFO  librespot] librespot 0.6.0 VERGEN_IDEMPOTENT_OUTPUT (Built on 2025-01-24, Build ID: jn3b7UuP, Profile: release)
[2025-01-24T16:07:44Z TRACE librespot] Command line argument(s):
[2025-01-24T16:07:44Z TRACE librespot]          verbose
[2025-01-24T16:07:44Z TRACE librespot]          name "librespot"
[2025-01-24T16:07:44Z DEBUG librespot_core::session] new Session
[2025-01-24T16:07:44Z DEBUG librespot_discovery::server] Zeroconf server listening on 0.0.0.0:37773
[2025-01-24T16:07:44Z INFO  librespot_playback::mixer::softmixer] Mixing with softvol and volume control: Log(60.0)
[2025-01-24T16:07:44Z DEBUG librespot_playback::player] new Player [0]
[2025-01-24T16:07:44Z INFO  librespot_playback::convert] Converting with ditherer: tpdf
[2025-01-24T16:07:44Z INFO  librespot_playback::audio_backend::rodio] Using Rodio sink with format S16 and cpal host: ALSA
[2025-01-24T16:07:44Z INFO  librespot_playback::audio_backend::rodio] Using audio device: default
[2025-01-24T16:07:44Z DEBUG librespot_playback::audio_backend::rodio] Rodio sink was created
[2025-01-24T16:07:49Z DEBUG librespot_discovery::server] POST "/" {}
[2025-01-24T16:07:49Z DEBUG librespot_core::session] Shutdown: Invalidating session
[2025-01-24T16:07:49Z DEBUG librespot::component] new MercuryManager
[2025-01-24T16:07:49Z DEBUG librespot::component] new ChannelManager
[2025-01-24T16:07:49Z DEBUG librespot_core::session] new Session
[2025-01-24T16:07:49Z DEBUG librespot_connect::spirc] new Spirc[0]
[2025-01-24T16:07:49Z DEBUG librespot::component] new MercuryManager
[2025-01-24T16:07:49Z DEBUG librespot::component] new SpClient
[2025-01-24T16:07:49Z DEBUG librespot_core::spclient] Client token unavailable or expired, requesting new token.
[2025-01-24T16:07:49Z DEBUG librespot_playback::player] command=SetSession
[2025-01-24T16:07:49Z DEBUG librespot_core::session] drop Session
[2025-01-24T16:07:49Z DEBUG librespot::component] drop ChannelManager
[2025-01-24T16:07:49Z DEBUG librespot::component] drop MercuryManager
[2025-01-24T16:07:49Z DEBUG librespot_core::http_client] Requesting https://clienttoken.spotify.com/v1/clienttoken
[2025-01-24T16:07:49Z DEBUG librespot_core::spclient] Received a granted token
[2025-01-24T16:07:49Z TRACE librespot_core::spclient] Got client token: GrantedTokenResponse { token: "xxx", expires_after_seconds: 1216800, refresh_after_seconds: 1209600, domains: [TokenDomain { domain: "spotify.com", special_fields: SpecialFields { unknown_fields: UnknownFields { fields: None }, cached_size: CachedSize { size: 0 } } }, TokenDomain { domain: "spotify.net", special_fields: SpecialFields { unknown_fields: UnknownFields { fields: None }, cached_size: CachedSize { size: 0 } } }], special_fields: SpecialFields { unknown_fields: UnknownFields { fields: None }, cached_size: CachedSize { size: 0 } } }
[2025-01-24T16:07:49Z DEBUG librespot::component] new ApResolver
[2025-01-24T16:07:49Z DEBUG librespot_core::http_client] Requesting https://apresolve.spotify.com/?type=accesspoint&type=dealer&type=spclient
[2025-01-24T16:07:49Z INFO  librespot_core::session] Connecting to AP "ap-gew4.spotify.com:4070"
[2025-01-24T16:08:22Z DEBUG librespot_discovery::server] POST "/" {}
[2025-01-24T16:08:52Z DEBUG librespot_discovery::server] POST "/" {}
[2025-01-24T16:09:22Z DEBUG librespot_discovery::server] POST "/" {}

Host (what you are running librespot on):

• OS: Ubuntu Desktop 22.04.5 LTS
• Platform: x86_64 Dell Laptop

Thanks in advance for your help. Please ask if you need more information.

[photovoltex]

Seems like it's getting stuck while opening the TCP connection to the access point. I suppose you can reproduce the issue reliable?

This sounds a bit similar to #1437. Could you check your cpu usage when you run into the issue?

An just some possible ways to get it working, which don't solve the underlying issue:

• using oauth instead of zeroconf (see https://github.com/librespot-org/librespot/wiki/Options#oauth)
• or use the latest dev version

[Timboooh]

I think you're right thinking it's TCP:

• CPU of librespot stays low (around min. 0.1% to max. 1.3%) when idle, shortly jumps to around 2.5% when connecting and then quickly goes back down to the same usage as the idle state. RAM usage stays low aswell.

• Enabling OAuth doesn't seem to work (oauth.log). Using this method the player also doesn't show up in the spotify clients.

• Using Dev branch doesn't seem to make a difference (tried both with and without oauth) (dev.log)

[kingosticks]

Are you sure you don't have a firewall blocking port 4070?

[Timboooh]

I feel stupid now, I was connected though my company's VPN which was probably blocking the TCP connections.
Disconnecting it seems to work
Sorry for taking up your time 🙃 , closing this issue

[kingosticks]

I used to have this exact same problem when I forgot I was connected through a VPN. And I sorted it with #1350 but that's weirdly not helping you.

edit: maybe the connection itself is established OK but then the Spotify handshake communication is blocked - we've no timeout for that. We could add logging, or move the timeout to also include the handshake. These things should be made easier to debug.