Each server instance knows exactly how many clients each server currently have.

branch "SMARTLINK" is continous be ok for smartlink project

Delete some fields in message defs, make master branch a "example" branch for study , also as a template for other new branches.

congratulations! a pin version, has been founded. this version, cross-svr cluster has been realized.

When cross-svr network established, servers will exchange their clients uuid info.
wen client log in, local svr will broadcast its uuid to remote svrs, when clients log out,
its uuid will be broadcasted again.

we have only one step left.--the real data hop.

It is very strange, that in GNU C++ in Ubuntu, inline-member funcs called by different thread will return zero values.