SendNegotiateProtocolVersion(List *unrecognized_protocol_options)
{
	StringInfoData buf;
	ListCell   *lc;

	pq_beginmessage(&buf, 'v'); /* NegotiateProtocolVersion */
	pq_sendint32(&buf, PG_PROTOCOL_LATEST);
	pq_sendint32(&buf, list_length(unrecognized_protocol_options));
	foreach(lc, unrecognized_protocol_options)
		pq_sendstring(&buf, lfirst(lc));
	pq_endmessage(&buf);

	/* no need to flush, some other message will follow */
}
Unknown