ffmpeg nonmatching transport in server reply

google ONE
I looked at the source for ffmpeg to see the relavent lines generating that
error to try and understand what exactly it might be having problems with,
but I do not quite understand what that is checking.

    /* Fail if the server responded with another lower transport mode
     * than what we requested. */
    if (reply->transports[0].lower_transport != lower_transport) {
        av_log(s, AV_LOG_ERROR, "Nonmatching transport in server reply\n");
        err = AVERROR_INVALIDDATA;
        goto fail;
    }