How to share variable in two C++ files

Question

I am trying a code which has two C++ files(client.cpp and server.cpp) and one common.h header file which contais a class and functions

Answer 1

in one and only one C file write (without extern) at main level (not in function)

int ch;

BUT not declare in main, beause the first will be hidden, You can set value

ch = 1;

but not declare;