info

Tag 20: a client asks what a server is; the server sends exactly one response carrying, as JSON, the revision of this specification it implements, 2.3.0, and the capabilities it holds out, and the scope finishes.

A client opens the scope with a request whose payload is the tag byte 20 and nothing more. The server sends exactly one response, whose payload is one JSON object carrying version, the string 2.3.0, the revision of this specification, and capabilities, the object the Capabilities layer defines. The response finish follows the response, and no frame follows the finish.

• The request. The request carries no parameter; the tag is the whole of it. Request states its form.
• The response. The response carries the string 2.3.0 as version, and a server that implements this revision sends no other string; it carries as capabilities the capabilities the server holds out. Response states its form.
• No error. This endpoint defines no error frame and no refusal. The scope carries exactly one response and the response finish.
• Independence. The request and its response depend on no other exchange. A client that does not know which revision a server implements, or which parts of the Endpoints layer it serves, learns both from this exchange before it composes any other request.
• The capabilities bind. The capabilities the response carries are a fact of the server: every info response the server sends, on every connection, carries the same capabilities, and the server serves every request on every connection as they state. Capabilities states what each capability binds the server to, and what the server sends for a request past a capability it does not hold out.