STUN client (ANSI C) for embedding in Embedded system?

Question

open source

You need a STUN client to embed in some Embedded System. The entire project is written in ANSI C.
What library would you recommend?
Library requirements:
— Open source;
- stable and proven;
- for a system written in ANSI C;
- easily (!) assembled under Linux (preferably also under Windows) "without a file";
- with a minimum development time, examples and high-quality documentation are desirable;
- compact.
With no less gratitude, I will accept advice / links / descriptions that help write your own STUN client (in case you can’t use the ready-made client).
Thanks in advance for the answers on the merits, personal experience is welcome.