by Darius Kazemi, July 23 2019

In 2019 I'm reading one RFC a day in chronological order starting from the very first one. More on this project here. There is a table of contents for all my RFC posts.

The socket czar's opening gambit

RFC-204 is titled “Sockets in use” and is authored by Jon Postel of UCLA. It's dated August 5, 1971.

The technical content

Jon Postel would like to know what sockets are being used for standard programs. This is because sockets, at least for initial connection for programs, need to be well-known. A socket number combined with a host site number forms a unique identifier that lets a computer program at site A connect to a computer program at site B.

Postel notes that RFC-196 suggests the use of socket 5 for the Mail Box Protocol, and he asks whether anyone objects, and if anyone has any suggestions about how to handle socket number assignments.

Further reading

By late 1973, Jon Postel would be affectionately called the “Socket Czar” by Bob Braden in RFC-599.

Just as socket numbers were needed to be agreed upon for different network programs in 1971, port numbers are needed to be agreed upon for different network programs in 2019. When you ask to connect to example.com over HTTPS, your browser looks up something like a host site number (IP address) and it knows ahead of time that the port, which is kind of like a socket, is number 443.

In a real sense, today's IANA Port Number Registry is the grandchild of an effort that began with this RFC.

How to follow this blog

You can subscribe to this blog's RSS feed or if you're on a federated ActivityPub social network like Mastodon or Pleroma you can search for the user “@365-rfcs@write.as” and follow it there.

About me

I'm Darius Kazemi. I'm an independent technologist and artist. I do a lot of work on the decentralized web with ActivityPub, including a Node.js reference implementation, an RSS-to-ActivityPub converter, and a fork of Mastodon, called Hometown. You can support my work via my Patreon.