How to receive events from custom FD added to event loop?

[notr1ch]

I have created a fairly basic uWS::SSLApp that has websocket clients listen to various topics. The messages I want to send for these topics arrive over UDP, so I would like to add a UDP socket to the event loop and publish based on data received from it. I create a socket, bind it, etc but I am getting stuck here:

struct us_loop_t *loop = (struct us_loop_t *) uWS::Loop::get();
struct us_poll_t *poll = us_create_poll (loop, 0, 0);
us_poll_init (poll, s, ???);
us_poll_start (poll, loop, ???);

/* Associate this poll with a socket descriptor and poll type */
WIN32_EXPORT void us_poll_init(struct us_poll_t *p, LIBUS_SOCKET_DESCRIPTOR fd, int poll_type);
/* Start, change and stop polling for events */
WIN32_EXPORT void us_poll_start(struct us_poll_t *p, struct us_loop_t *loop, int events);

What should poll_type and events be? I thought I should use POLL_TYPE_POLLING_IN and LIBUS_SOCKET_READABLE but these don't appear to be part of the libusockets.h public header.

Also after starting the poll, how / where I do I receive the events and read the data in the uWS::SSLApp loop?