The L2CAP functionality is currently available for BTPROTO_L2CAP sockets only. An interface to higher protocol layers, such as RFCOMM, or for future developments that will allow you to run TCP/IP directly over L2CAP, was not available in the Linux kernel implementation at the time of writing. However, the L2CAP sockets allow you to install these protocols in the user space. The SDP (Service Discovery Protocol) protocol is not integrated in the Linux kernel either. RFCOMM might be implemented in the kernel in the future, but this is currently not intended for SDP.
