The IETF April Fools' protocol for controlling coffee pots over HTTP is HTCPCP, the Hyper Text Coffee Pot Control Protocol. It was specified in RFC 2324, published on 1 April 1998 as a deliberately humorous Internet standard.
Written by Larry Masinter, the RFC satirized the tendency to extend HTTP to every imaginable device. HTCPCP uses playful additions to ordinary web concepts: a coffee-pot URI scheme, a BREW method, and an Accept-Additions header for options such as cream, milk, or whisky. Its fake technical seriousness is part of the joke.
The protocol also popularized the association between coffee pots and HTTP status code 418, “I'm a teapot.” That response was intended for a teapot asked to brew coffee, not as a normal coffee-machine error. The specification even includes whimsical discussion of coffee freshness and networked brewing behavior.
The joke later received a tea-themed sequel. RFC 7168, published on 1 April 2014, extended the concept with HTCPCP-TEA for tea efflux appliances. Neither Gopher, WebDAV, nor SMTP serves this fictional coffee-control role.