Bob Metcalfe’s article

The first published reference to the world’s first webcam happened before it was a webcam!

On January 27, 1992, Bob Metcalfe’s column in Communications Week talked about our XCoffee system, which, the following year, would be connected to the web using a gateway created by Dan Gordon and Martyn Johnson. CommWeek is now long-gone, but I found a copy of the column in my emails from the period, and it’s reproduced here with Bob’s kind permission.

Communications Week (USA)
January 27, 1992
Bob Metcalfe’s LAN Notes

Hacking a New ATM-RPC-Ethernet Coffee Pot Server

Like hackers immemorial, surrounded by the toys required for serious computer research, Quentin Stafford-Fraser and Paul Jardetzky here at the University of Cambridge could not resist spending a few recent nights hacking together an unauthorized network application called XCoffee.

Such just-for-fun hacks can stir up the unexpected and, sometimes, important ideas for new killer apps.

Quentin and Paul wrote XCoffee so that while sitting at their networked workstations they can see the coffee pot shared with colleagues in the lab’s office tower. The computer laboratory is littered with cheap video cameras as a result of its Pandora Project (which I will report on soon). They commandeered a spare camera and aimed it at the coffee pot from a rack-mounted video-frame-grabbing 68020 server.

Now, from the comfort of their offices, users can see the tower’s coffee pot, its power light, and the level and darkness of the coffee. They glance at the small XCoffee window on their displays and, applying a bit of game theory, decide when to run down the tower cup in hand.

XCoffee uses asynchronous transfer mode (ATM) remote procedure calls (RPC) over Ethernet to grab 768x576x8-bit monochrome pictures of the coffee pot. It then uses the Massachusetts Institute of Technology’s X Window System over Ethernet to put selected versions of those pictures on user displays.

You may be confused by the mention in such a simple application of RPC over ATM, and of ATM over Ethernet. The lab has for years been experimenting with high-grade multimedia communications, including real-time desk-top videoconferencing. The ATM rings and switches work up to 500 megabits per second. They include elaborate distributed system software facilities such as RPC. XCoffee exploits this classy environment only because it is lying around. Since XCoffee requires low-resolution still pictures every few seconds, even Ethernet is gross overkill -- RS232 would do.

With this coffee pot application now well on its way to market, Quentin and Paul are thinking about follow-on … well, err, hacks. Possibilities include adding color and networked-camera applications that let them watch the queue in the tea room, the paper trays on printers, and the sandwich van in the parking lot.

Why not extend XCoffee to image-process its pictures of the coffee pot so that it can sound an alarm when the pot nears empty? Why not let users reserve a cup of coffee while running down the tower cup in hand? The possibilities are endless.

XCoffee is the best network appliance hack I’ve heard about since the Simple Network Management Protocol-managed toaster demonstrated at Interop a year ago. You might reasonably conclude from such hacks that certain programmers don’t have enough worthwhile to keep them busy. But I conclude that there are things new under the sun, and that we still need hackers to find them.

BOB METCALFE hacked Arpanet at MIT Project Mac just before inventing Ethernet at Xerox Parc in 1973. Comments are welcome via the Internet to The opinions expressed are his own.