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Questions tagged [l2cap]

Bluetooth Logical link control and adaptation protocol resides in the data link layer.

L2CAP is used within the Bluetooth protocol stack. It passes packets to either the Host Controller Interface (HCI) or on a hostless system, directly to the Link Manager/ACL link. L2CAP provides connection-oriented and connectionless data services to upper layer protocols with protocol multiplexing capability, segmentation and reassembly operation, and group abstractions. L2CAP permits higher level protocols and applications to transmit and receive L2CAP data packets up to 64 kilobytes in length.

L2CAP's functions include:

  • Multiplexing data between different higher layer protocols.
  • Segmentation and reassembly of packets.
  • Providing one-way transmission management of multicast data to a group of other Bluetooth devices.
  • Quality of service (QoS) management for higher layer protocols.
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When did the L2CAP SMP channel create?

I try to understand the BLE pairing procedure via checking the HCI log and reading the Core profile . now I know something as blow : 1.SMP use the channel 0x0006 in L2CAP. 2.L2CAP has the connectionless\Connection-oriented channel , 0x0006 belongs…
jiapeng.ye
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iOS L2CAP/GATT- throughput

I'm trying to achieve high throughput over iPhone with my device (using gatt or l2cap). For L2cap: I used https://github.com/bluekitchen/CBL2CAPChannel-Demo/blob/master/CBL2CAPChannel-Demo/BKL2CAPClient.m on my iphone, and a test from bluekitchen…
justme
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Timed Out when connecting to device via L2CAP bluetooth socket, when LTE chip is integrated

I'm experiencing a strange issue with one of my applications: Background: One of my features requires Bluetooth connectivity. Once a device (i.e. phone) is paired with the host, I continuously "poll" the device, to extract the RSSI (signal…
Sash
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CBL2CAPChannel not responsive while app is backgrounded

I'm facing an issue where L2CAP (or NSStream) stops notifying events to the app after app went to background (after 2-10 seconds). App is probably being suspended (as expected). My expectation is that when there's BLE activity, app should be awaken…
Pawel Klapuch
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How is Data Length Extension (DLE) enabled for BLE?

How is data length extension enabled? I have BlueZ on a Raspberry Pi 4B (the peripheral). I want to maximise my L2CAP channel throughput and hence want to move from a data channel payload of 27 bytes to 251. Is there a way to do this similar to how…
Kelvin Lee
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NSStream (BLE L2CAP) on background thread

I'm looking for some verification of what i'm doing. Also, there's a lot of related topics here and there but none is complete / addresses all challenges. Overview / Requirements: BLE (L2CAP) Central able to talk to multiply simultaneously…
Pawel Klapuch
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Why are there two different socket options (RFCOMM and L2CAP) in BlueZ?

I'm doing bluetooth socket programming, and I have few questions about sockets provided by BlueZ. When we're dealing with TCP/IP socket programming, we can usually choose either TCP or UDP as our transport protocol. As far as I know, these two…
KaiwenJon
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Bluez L2CAP CoC to Android / iOS Credit based flow failing

I've been trying to get a connection from Android using createL2capChannel or createInsecureL2capChannel (and iOS) to a Raspberry Pi which has created a BTPROTO_L2CAP SOCK_SEQPACKET Bluetooth socket which it is accepting, running Bluez 5.50 but they…
meavydev
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What is a preferred PSM in the wdf windows example?

I've been studying the echo bit sample from WDF Windows. There is a function BthEchoSrvRegisterPSM in server.c which registers PSM. It looks like that: _IRQL_requires_max_(PASSIVE_LEVEL) NTSTATUS BthEchoSrvRegisterPSM( _In_…
user
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A difference between Service GUID and a server name and a service class in Bluetooth

I've been studing the bluetooth echo server example from windows wdf samples. I want to understand the l2cap bt driver implementation, but I'm still a bit confused. Below I listed the code from the example. Here we have a GUID and a name of a…
user
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Android bluetooth communication access modes?

When I check the bluetooth developer page, it states very clearly that the android api supports the establishment of RFcomm channels. Now, is this mode exclussive for android or does android also support HCI or Bnep (more specifically l2cap)? (Or am…
ahodder
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Can L2CapChannel from IOBluetooth framework in MacOS commentate with L2capChannel in Core Bluetooth framework in iOS

I am trying to communicate between Mac OS and iOS for sending data back and forth.In Mac OS IOBluetooth framework provides L2cap channel but when I open it and use iOS Core Bluetooth L2CAP it doesnt connect to the channel.How do I make them work as…
md12
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L2CAP channel, bytes sent but not arriving

In an iOS app I am making an audio file transfer using CoreBlueTooth L2CAP channel, between one device and another one. It is already half working but not yet entirely. At this point I have transferred the file name, but coming to the file contents,…
Michel
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Trying to understand L2CAP channel

Now facing some challenges using CoreBlueTooth L2CAP channel. In order to better understand how things work. I have taken the L2CapDemo (master) (https://github.com/paulw11/L2CapDemo) from GitHub and tried to experiment with it. Here is what I have…
Michel
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Using CoreBlueTooth L2CAP channel to transfer an audio file

I need some sample code to see how to transfer an audio file (or any other binary data) using CoreBlueTooth L2CAP channel. Assuming the file is not so small, let us say it is a few hundred kilobytes. I am working on a small iOS app doing that, but…
Michel
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