RFComm

RFCOMM

frame types

  - SABM (Set Asynchronous Balanced Mode command)

    : connect with remote server channel

  - UA (Unnumbered Acknowledgement response)

    : response for SABM/DISC

  - DM (Disconnected Mode response)

    : when RFCOMM is disconnected

  - DISC (Disconnect command)

    : disconnect with remote device

  - UIH (Unnumbered information with header check command and response)

    : send and receive data with remote device.

SCN(Server Channel Number)

Server applications registering with an RFCOMM service interface are assigned a 

Server Channel number in the range 1…30. [0 and 31 should not be used since 

the corresponding DLCIs are reserved in TS 07.10] It is this value that should be 

registered in the Service Discovery Database.

  - MAP, PBAP, HFP can obtain SCN from  SDP.

  - SCN 0 means  control channel.

Supported Control Channel Commands

 - DLC parameter negotiation (PN)

DLCI (Data Link Connection Identifier) 

  - DLCI 0 : control 

  - DLCI even : initializing connection

  - DLCI odd : non-initializing connection

DISC (Disconnect command) 

The DISC command shall be used to terminate an operational or initialization mode previously set by a command. It

shall be used to inform one station that the other station is suspending operation and that the station should assume a

logically disconnected mode. Prior to actioning the command, the receiving station shall confirm the acceptance of the

DISC command by the transmission of a UA response.

UA (Unnumbered Acknowledgement) response

The UA response shall be used by the station to acknowledge the receipt and acceptance of SABM and DISC commands.

C/R (Command/Response)

The C/R (command/response) bit identifies the frame as either a command or a response.

P/F (Poll/Final)

The poll (P) bit set to 1 shall be used by a station to solicit (poll) a response or sequence of responses from the other station.

The final (F) bit set to 1 shall be used by a station to indicate the response frame transmitted as the result of a soliciting (poll) command.