The Finger protocol is extremely simple. It was created in 1971 by Les Earnest as a way to get information about who was logged in on a remote server, and and what they were working on. By the late 1990s it had gone out of favor as it had been superceded by more secure protocols and the World Wide Web.

Here is a minimal example of the Finger protocol implemented in Python 3.

Server

It runs over TCP on port 79 and essentially consists of one request and one response. When the client opens a socket to the server, it sends a plaintext string (terminated with a CRLF aka \r\n) containing the name of the user to query. If the user is found on the server's system, the system should return any information about the user that the system administrator deems fit to send. This could include last login time, number of unread emails, their telephone number, or none of the above. Immediately following this information should be the contents of the user's .plan file in their home directory. This file can can be used as a form of microblogging, to-do lists, or simply note taking that other people are allowed to view.

There is only one recognized option switch in the protocol. If the username is prefixed with /W and a space, the server is expected to deliver more verbose information about the requested user.

Naturally, this is a very flexible standard. The daemon running on port 79 could theoretically return anything, though it is expected to reutrn some kind of plaintext document written by the requested user (presumably a .plan).

The original protocol used ASCII encoding by necessecity, but a modern implementation could probably get away with using UTF-8.

It is also extremely paramount that both the server and client programs be made secure from buffer overflow attacks. See the Morris worm.

Client

The client is also extremely simple. It is traditionally used from the command line, with the name finger. The syntax for a finger command is as follows:

finger username@hostname

The client program is then expected to resolve hostname to a web address, and then send username as the plaintext string to that address on port 79.

If you wish to get a more verbose answer from the server, the following syntax should be used:

finger "/W username@hostname"