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The RFCOMM protocol is used for the cable replacement option in Bluetooth. It is a simple transport protocol with additional provisions for emulating the 9 circuits of RS232 serial ports over L2CAP part of the Bluetooth protocol stack. It supports large base for applications that uses serial communication. It provides a reliable data stream, multiple connections, flow control and serial cable line settings. There are two types of devices that can be connected using RFCOMM
Device 1 -are the communication end points such as computers and printers.
Device 2 -are those that are part of communication segment
Service Discovery Protocol (SDP)
SDP is the basis for discovery of services on all Bluetooth devices. This is essential for all Bluetooth models because with SDP device information, services and the characteristics of the services can be queried and after that connection between two or more Bluetooth devices may be established .Other service discovery protocols such as Jini, UpnP etc. maybe used in conjunction with the Bluetooth SDP protocol.
Audio/video control transport protocol (AVCTP)
The music control buttons on a stereo headset use this protocol to control the music player. It is used by remote control to transfer AV/C commands over an L2CAP channel. In the protocol stack, AVCTP is bound to L2CAP.
Audio/video data transport protocol (AVDTP)
It is also bound to L2CAP layer to be used by advance audio distribution to stream music to stereo headsets over L2CAP layer.
Object exchange (OBEX)
OBEX is a session protocol defined by IrDA. This protocol is also utilized by Bluetooth thus enabling the possibility for application to use either the Bluetooth radio or IrDA technologies.
It is a specification which decides the way in which a device uses a Bluetooth technology. The profile provides standards which manufacturers follow to allow devices to use Bluetooth in an intended parameter. A Bluetooth profile resides on top of the Bluetooth Core Specification and (optionally) additional protocols. While the profile may use certain features of the core specification, specific versions of profiles are rarely tied to specific versions of the core specification. For example, there are HFP1.5 implementations using both Bluetooth 2.0 and Bluetooth 1.2 core specifications. Examples of profiles are
Low Energy Attribute Protocol (ATT)
It is similar to SDP but specially adapted and simplified for Low Energy Bluetooth. It allows a client to read and/or write certain attributes exposed by the server in a non-complex, low-power friendly manner. Bound to L2CAP.
Low Energy Security Manager Protocol (SMP)
This is used by Bluetooth Low Energy Implementations for pairing and transport specific key distribution. In the protocol stack, SMP is bound to L2CAP.