C unicode to ascii

I want to convert in C a string that is in unicode to ascii. My problem is that I'm trying to find in the tcp payload of a packet the string POST of a packet but I can't find it because probably it's utf-8 encoded. I know that there are more unicode characters of ascii one but I think that the problem is that.. I've found something for C# but do you kn开发者_运维百科ow if exist something for C?

If you're looking for "POST", this is the advantage of UTF-8. ASCII strings in UTF-8 are only represented by themselves.