#include <nng/nng.h>
typedef int32_t nng_duration;
#define NNG_DURATION_INFINITE (-1)
#define NNG_DURATION_DEFAULT (-2)
#define NNG_DURATION_ZERO (0)An nng_duration is a relative time, measured in
milliseconds.
This type is most often used in conjunction with timers and timeouts.
A couple of special values have been set aside, and carry special meanings.
NNG_DURATION_DEFAULT-
Indicates a context-specific default value should be used.
NNG_DURATION_INFINITE-
Effectively an infinite duration; used most often to disable timeouts.
NNG_DURATION_ZERO-
Zero length duration; used to perform a single polling operation.