Listing 4 in C

#ifndef ZMQ_DONTWAIT
# define ZMQ_DONTWAIT ZMQ_NOBLOCK
#endif
#if ZMQ_VERSION_MAJOR == 2
# define zmq_msg_send(msg,sock,opt) zmq_send (sock, msg, opt)
# define zmq_msg_recv(msg,sock,opt) zmq_recv (sock, msg, opt)
# define zmq_ctx_destroy(context) zmq_term(context)
# define ZMQ_POLL_MSEC 1000
// zmq_poll is usec
# define ZMQ_SNDHWM ZMQ_HWM
# define ZMQ_RCVHWM ZMQ_HWM
#elif ZMQ_VERSION_MAJOR == 3
# define ZMQ_POLL_MSEC 1
// zmq_poll is msec
#endif