how to know if some wireless device is nearby?

[Lisa000]

(c/c++programe in Linux)

[kestrel]

(c/c++programe in Linux)

Can you please give us more informaton?

[Lisa000]

I want to implement this function:

when wireless notebook A finds wireless notebook B is nearby, it will send a message to B, otherwise, it does nothing. I heard I can use wireless API in windows. But I want to find some c/c++ functions under Linux. Thanks.