Nut/OS is an intentionally simple RTOS for the ATmega128, which provides a minimum of services to run Nut/Net, the TCP/IP stack.
- Non preemptive multithreading.
- Periodic and one-shot timers.
- Dynamic heap memory allocation.
- Interrupt driven streaming I/O.
- Base protocols ARP, IP, ICMP, UDP and TCP.
- User protocols DHCP, DNS and HTTP.
- Socket API.
- Host, net and default routing.
- Interrupt driven Ethernet driver.
Source code: https://sourceforge.net/projects/ethernut/