private boolean isSettingsFrame(ByteBuf in) {
            final int start = in.readerIndex();
            return in.getByte(start + 3) == 4 &&             // type == SETTINGS
                   (in.getInt(start + 5) & 0x7FFFFFFF) == 0; // streamId == 0
        }
A handler that closes an HTTP/2 connection when the server responds with an HTTP/1 response, so that
HTTP/1 is used instead of HTTP/2 on next connection attempt.
core/src/main/java/com/linecorp/armeria/client/HttpClientPipelineConfigurator.java