I looked at BLE on google and it was inconclusive. I'm only an author of an app that uses bluetooth so while I know a little your question does not lend itself to being researched.
I have two CSR4.0 usb dongle and want to send l2cap packets from one to the other in the type of LE(low energy). What I can do now is using "hcitool leadv" to advertise the LE advertisement and using "hcitool lecc" to connect it. I can't find any APIs of l2cap to establish a connection between thses dongles. Is there any way to solve this problem?