Contiki

"Contiki is an open source operating system for the Internet of Things. Contiki connects tiny low-cost, low-power microcontrollers to the Internet. Contiki is a powerful toolbox for building complex wireless systems.

Contiki provides powerful low-power Internet communication. Contiki supports fully standard IPv6 and IPv4, along with the recent low-power wireless standards: 6lowpan, RPL, CoAP. With Contiki's ContikiMAC and sleepy routers, even wireless routers can be battery-operated.

Contiki supports per-process optional preemptive multithreading, inter-process communication using message passing through events, as well as an optional graphical user interface (GUI) subsystem with either direct graphic support for locally connected terminals or networked virtual display with Virtual Network Computing (VNC) or over Telnet.
A full installation of Contiki includes the following features:

• Multitasking kernel
• Optional per-application preemptive multithreading
• Protothreads
• Internet Protocol Suite (TCP/IP) networking, including IPv6
• Windowing system and GUI
• Networked remote display using Virtual Network Computing
• A web browser (claimed to be the world's smallest)
• Personal web server
• Simple telnet client
• Screensaver

http://www.contiki-os.org/

https://en.wikipedia.org/wiki/Contiki