CURLINFO_RTSP_CSEQ_RECV man page
CURLINFO_RTSP_CSEQ_RECV — get the recently received CSeq
CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_RTSP_CSEQ_RECV, long *cseq);
Pass a pointer to a long to receive the most recently received CSeq from the server. If your application encounters a CURLE_RTSP_CSEQ_ERROR then you may wish to troubleshoot and/or fix the CSeq mismatch by peeking at this value.
Added in 7.20.0
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.