mqtt client id

[kushal bhattacharya via Digitalmars-d-learn]

hi,
I am totally following what hivemq and mqtt specs are telling.But 
i have confusion regarding their implementation.In mqtt specs 
they are suggesing to generate random client id if cleansession 
flag is true and  not for cleansession flag being false.My 
question is how do i really implement this on my area of 
programming language.To be more specific am working in linux 
command line and my programming language is c++.