Module rfcomm 

Bluetooth RFCOMM (Serial Port Emulation Protocol)

Implements the RFCOMM multiplexer protocol over L2CAP (PSM 0x0003), providing RS-232 serial port emulation. Supports credit-based flow control, FCS computation, modem status commands, and DLCI-based multiplexing for multiple simultaneous serial connections.

Reference: Bluetooth Core Specification v5.4, RFCOMM with TS 07.10

Structs

CreditFlowControl

Credit-based flow control state for an RFCOMM channel

ModemSignals

Modem signal bits for MSC (Modem Status Command)

RfcommChannel

An RFCOMM data channel (one per DLCI)

RfcommFrame

An RFCOMM frame

RfcommMultiplexer

RFCOMM multiplexer: manages all channels over a single L2CAP connection

Enums

ChannelState

RFCOMM channel state

MuxCommandType

RFCOMM multiplexer control command types

Constants

DEFAULT_INITIAL_CREDITS

Default initial credits for credit-based flow control

DLCI_CONTROL

DLCI 0 is the multiplexer control channel

FRAME_DISC

DISC (Disconnect) - disconnect request

FRAME_DM

DM (Disconnected Mode) - rejection / channel not available

FRAME_SABM

SABM (Set Asynchronous Balanced Mode) - connection establishment

FRAME_UA

UA (Unnumbered Acknowledgement) - acknowledgement

FRAME_UIH

UIH (Unnumbered Information with Header check) - data transfer

MAX_DLCI

Maximum DLCI value (5 bits, 0-30 usable; 31 reserved)

RFCOMM_DEFAULT_MTU

Default RFCOMM MTU (maximum frame size, N1)

RFCOMM_MAX_FRAME_DATA

Maximum RFCOMM frame data size for fixed-size buffers

RFCOMM_MAX_MTU

Maximum RFCOMM MTU

RFCOMM_PSM

L2CAP PSM for RFCOMM

Functions

calculate_fcs

Calculate FCS over a byte slice

decode_cr

Decode the C/R bit from an RFCOMM address byte

decode_dlci

Decode the DLCI from an RFCOMM address byte

encode_address

Encode the RFCOMM address byte from DLCI, C/R bit, and EA bit

verify_fcs

Verify FCS: compute over data + fcs byte, result should be 0xCF