RFC 866

Active Users 💖

okay bestie, this is RFC 866 🎀 by J. Postel at ISI, dated May 1983 🌸. It's a standard ✨ (it literally says it specifies a standard for the ARPA Internet community), and it doesn't list anything it obsoletes or updates, so it's giving clean slate 🧚. Hosts on the ARPA Internet that choose to implement an Active Users Protocol are expected to adopt and implement this standard 💅.

A useful debugging and measurement tool is an active users service 🔥. It just sends back a list of the currently active users on the host, no matter what you sent it 🙈.

An active user is someone logged in, like the people listed in SYSTAT or WHO 👑.

TCP Based Active Users Service

One active users service is defined as a connection based application on TCP 🦋. A server listens for TCP connections on TCP port 11 👂. Once a connection is established, the list of currently active users gets sent out that connection, and any data received is thrown away 💀. The service closes the connection after sending the list ✨.

UDP Based Active Users Service

Another active users service is defined as a datagram based application on UDP 🌈. A server listens for UDP datagrams on UDP port 11. When a datagram is received, an answering datagram is sent containing a list of the currently active users, and the data in the received datagram is ignored 🫶.

If the list doesn't fit in one datagram, send a sequence of datagrams, but don't break the information for a user (a line) across a datagram 😭. The user side should wait for a timeout for all datagrams to arrive 🍓. Note that they are not necessarily in order 🙈.

User List Syntax

There is no specific syntax for the user list 🌸. It is recommended that it be limited to the ASCII printing characters, space, carriage return, and line feed 💜. Each user should be listed on a separate line 🎀.