int nghttp2_submit_ping(nghttp2_session *session, uint8_t flags, const uint8_t *opaque_data)
Submits PING frame. You don't have to send PING back when you received PING frame. The library automatically submits PING frame in this case.
The flags is bitwise OR of 0 or more of the following value.
If the opaque_data is non
NULL, then it should point to the 8 bytes array of memory to specify opaque data to send with PING frame. If the opaque_data is
NULL, zero-cleared 8 bytes will be sent as opaque data.
This function returns 0 if it succeeds, or one of the following negative error codes:
Out of memory.