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9.8 Supported Bluetooth Profiles Overview
9.8.1 RFCOMM with TS07.10
The RFCOMM protocol emulates the serial cable line settings and status of an RS-232
serial port and is used for providing serial data transfer. RFCOMM connects to the lower
layers of the Bluetooth protocol stack through the L2CAP layer.
By providing serial-port emulation, RFCOMM supports legacy serial-port applications while
also supporting the OBEX protocol among others. RFCOMM is a subset of the ETSI TS
07.10 standard, along with some
Bluetooth specific adaptations.
The RFCOMM protocol supports up to 60 simultaneous connections between two Bluetooth
devices. The number of connections that can be used simultaneously in a Bluetooth device
is implementation-specific.
For the purposes of RFCOMM, a complete communication path involves two applications
running on different devices (the communication endpoints) with a communication
segment between them. The figure above shows the complete communication path. (In
this context, the term application may mean other things than end-user application; e.g.
higher layer protocols or other services acting on behalf of end-user applications.)
RFCOMM is intended to cover applications that make use of the serial ports of the devices
in which they reside. In the simple configuration, the communication segment is a
Bluetooth link from one device to another (direct connect), see the figure to the left.
Where the communication segment is another network, Bluetooth wireless technology is
used for the path between the device and a network connection device like a modem.
RFCOMM is only concerned with the connection between the devices in the direct connect
case, or between the device and a modem in the network case.
RFCOMM can support other configurations, such as modules that communicate via
Bluetooth wireless technology on one side and provide a wired interface on the other side,
as shown in the figure below. These devices are not really modems but offer a similar
service. They are therefore not explicitly discussed here.
Basically two device types exist that RFCOMM must accommodate. Type 1 devices are
communication end points such as computers and printers. Type 2 devices are those that
are part of the communication segment; e.g. modems. Though RFCOMM does not make a
distinction between these two device types in the protocol, accommodating both types of
devices impacts the RFCOMM protocol.
Source: Bluetooth SIG, URL:
http://www.bluetooth.com/Bluetooth/Technology/Works/RFCOMM.htm
9.8.2 Service Discovery Protocol (SDP)
SDAP describes how an application should use SDP to discover services on a remote
device. It illustrates several approaches to managing the device discovery via Inquiry and
Inquiry Scan and service discovery via SDP. The ideas contained in the SDAP specification
augment the basic specifications provided in GAP, SDP, and the basic processes of device
discovery. The use cases for SDAP are intended to encompass the majority of service
discovery scenarios associated with all profiles and devices.
Source: Bluetooth SIG, URL:
http://www.bluetooth.com/Bluetooth/Technology/Works/SDAP.htm