I am looking forward to implement messaging protocols in Arduino device. Most of the time the embedded systems will be client of some remote server and they will be communicating to this remote server using the these IoT protocols.
MQTT was trivial but other protocols aren't easily portable like I found no Arduino support for CoAP.
What are other protocols that can be embedded in Arduino (Yun)?
I found a workaround specifically for Yun and considered myself answering this question. You can simply import library in the Linux (Linino) side of Yun by accessing the root.
ssh root@<yunaddress>
Use Python to create/import repository for the library you want for some specific protocol. To install some package like python, use:
opkg install <packagename>
If you want to work with C/C++ libraries, work with:
$ opkg install yun-gcc
$ opkg install make
Good luck!