#include <nng/nng.h> int nng_pipe_id(nng_pipe p);
nng_pipe_id() function returns a positive identifier for the pipe p,
if it is valid.
Otherwise it returns
A pipe is considered valid if it was ever created by the socket.
Pipes that are allocated on the stack or statically should be
initialized with the macro
This function returns the positive value for the pipe identifier, or
-1 if the pipe is invalid.