Http2 Pri Method Probe

A request using the PRI method, typically sent as PRI * HTTP/2.0, which is the HTTP/2 connection preface. This primitive indicates protocol negotiation probing where a scanner tests whether the service supports HTTP/2 or how it handles unexpected protocol upgrades. When observed against Elasticsearch ports, it usually represents generic HTTP stack fingerprinting rather than legitimate Elasticsearch interaction, helping the client determine server capabilities, proxy behavior, or error handling characteristics.