SDPD(8)

💙 SDPD(8) — Bluetooth Service Discovery Protocol daemon

okay so real talk, bestie: this is the sdpd page from the System Manager's Manual and it's basically the wingman of your whole Bluetooth setup. let me walk you through it 🫶

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✨ SYNOPSIS ✨

sdpd [-dh] [-c path] [-g group] [-u user]

that's it. that's the whole vibe. 🎀

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💅 DESCRIPTION 💅

The sdpd daemon keeps track of the Bluetooth services registered on the host and responds to Service Discovery inquiries from the remote Bluetooth devices.

like, it's the little gremlin in the background that knows exactly what your machine can do over Bluetooth, and it answers questions about it. iconic behavior, honestly. 👑

So here's the tea ☕ — in order to use any service, a remote Bluetooth device needs to send a Service Search and Service Attribute request, or a Service Search Attribute request over a Bluetooth L2CAP connection on SDP PSM (0x0001). The sdpd daemon will try to find the matching Service Record in its Service Database and will send the appropriate response back. The remote device then processes the response, extracts all the required info, and makes a separate connection in order to actually use the service.

no cap, it's giving matchmaker energy. 🌸

Bluetooth applications running on the host register services with the local sdpd daemon. Operations like service registration, service removal and service change are performed over the control socket. And yes bestie, you can query the entire content of the sdpd Service Database with sdpcontrol(8) by issuing the browse command on the control socket. literally so satisfying to just look at everything ✨

The command line options are as follows:

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⭐ OPTIONS ⭐

• -d — Do not detach from the controlling terminal. lowkey useful when you wanna watch it do its thing 👀
• -c path — Specify the path to the control socket. The default path is /var/run/sdp. 🐚
• -g group — Specifies the group the sdpd should run as after it initializes. The value specified may be either a group name or a numeric group ID. This only works if sdpd was started as root. The default group name is nobody. 💜
• -h — Display usage message and exit. the classic "help me help you" move 🙈
• -u user — Specifies the user the sdpd should run as after it initializes. The value specified may be either a user name or a numeric user ID. This only works if sdpd was started as root. The default user name is nobody. 🧚

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🎀 FILES 🎀

• /var/run/sdp

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🦋 SEE ALSO 🦋

• sdp(3)
• sdpcontrol(8)

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👑 AUTHORS 👑

Maksim Yevmenkin <m_evmenkin@yahoo.com> — thank you for your service, legend 🫶

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🔥 CAVEATS 🔥

okay bestie, pay attention, this part is important:

• The sdpd daemon will listen for incoming L2CAP connections on a wildcard BD_ADDR. 🌈
• In case of multiple Bluetooth devices connected to the same host, it is possible to specify which services should be "bound" to which Bluetooth device. Such assignment should be done at service registration time. 💫
• Requests to register, remove or change service can only be made via the control socket. The sdpd daemon will check the peer's credentials and will only accept the request if the application has the same effective user ID as the root user ID. so like, no sneaky business 💀
• The sdpd daemon does not check for duplicated Service Records. It only performs minimal checking on the service data sent in the Service Register request. It is assumed that the application must obtain all required resources such as RFCOMM channels etc., before registering the service. fr fr, that's on you 🙈

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💀 BUGS 💀

Most likely. Please report if found. 😭 (i know. i know. it's giving chaos but at least they're honest about it 🍓)

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and that's the whole page, bestie! 🌟 this one's from Debian, dated January 13, 2004 — vintage but still slaying 💅 mwah 💖