lcox74/Gopher

A study on the gopher protocol

Gopher

2nd September 2021

Gopher is a protocol created around 1991 but a team of people at the University of Minnesota. It's a very light internet protocol that was killed off swiftly after the release of the World Wide Web (www). It's light in the sense that it was mainly used for read-only documentation distribution and functioned/looked very much like a file system. This allowed Gopher to be compatiable with working in terminal based computers.

This current repo/project is just a study on the network protocol and trying to develop a client and server application as a challenge to myself to learn new things and see how things were done before my time. The spec I am following for this project is via the IETF datatracker; RFC 1436. I'll be starting with a terminal based client application and test it with any servers that still actively use the protocol like: gopher://gopher.floodgap.com/gopher (http proxy).

How does Gopher work

Unlike http:// using port 80, Gopher (gopher://) uses port 70 as its default port. But similarly still uses TCP for requests. The client and server interact as follows:

1. Client connects to server (i.e. gopher.floodgap.com) on port 70.
2. Server accepts.
3. Client sends a selector (i.e. /gopher) or just an empty line to see what selectors the server has.
4. Server sends back a response and closes the connection.

The response the server gives back follows a strict format, with each item the in the response is on a new line (CRLF):

Item Type (single character)	Display String	Selector	Hostname	Port
1	Floodgap Systems gopher root	/	gopher.floodgap.com	70
0	Does this gopher menu look correct?	/gopher/proxy	gopher.floodgap.com	70

Each row is a single item, and each item is made up of 5 different fields each seperated in the response via a tab (\t). The last row in the response is denoted by a single period (.) saying that there are no more items. The following is a filtered raw dump of the request broken down in steps above:

1Floodgap Systems gopher root	/	gopher.floodgap.com	70
0Does this gopher menu look correct?	/gopher/proxy	gopher.floodgap.com	70
0A Brief Introduction to Gopherspace -- READ ME FIRST!	/gopher/welcome	gopher.floodgap.com	70
0Why is gopher still relevant?	/gopher/relevance.txt	gopher.floodgap.com	70
0Robert Bigelow: Gopher & Gopherspace	/users/rbigelo/gopher.txt	sdf.org	70
0Wired 08/2010: The Web Is Dead. Long Live The Internet.	/gopher/webisdead.txt	gopher.floodgap.com	70
0The creators of Gopherspace at UMN (Star Tribune 11/5/01)	/gopher/StarTribune.txt	gopher.floodgap.com	70
0Using your web browser to explore Gopherspace	/gopher/wbgopher	gopher.floodgap.com	70
1The Overbite Project: Gopher clients for mobile and desktop (OverbiteWX, OverbiteNX, Overbite Android)	/overbite	gopher.floodgap.com	70
1Patches and clients for other legacy platforms	/gopher/clients	gopher.floodgap.com	70
1The SDF Member PHLOGOSPHERE		phlogosphere.org	70
1The Bucktooth gopher server	/buck	gopher.floodgap.com	70
1The Gopher Toybox: sample gophermaps to create your own server	/gopher/toybox	gopher.floodgap.com	70
1Floodgap Gopher Shortener Service	/gopher/shorten	fld.gp	70
1New gopher servers since 1999	/new	gopher.floodgap.com	70
1Technical specifications, RFCs, documents	/gopher/tech	gopher.floodgap.com	70
0"In The Beginning Was The Command Line"	/gopher/itbwtcl	gopher.floodgap.com	70
.

I mention just before that this was a filtered raw dump, I say this because there are items that had a non-canonical type denoted as i for the item type. My implementation will only be supporting cannonical types, which are listed below:

Character	Description
0	Text file
1	Gopher submenu
2	CCSO Nameserver
3	Error code returned by a Gopher server to indicate failure
4	BinHex-encoded file (primarily for Macintosh computers)
5	DOS file
6	uuencoded file
7	Gopher full-text search
8	Telnet
9	Binary file
+	Mirror or alternate server (for load balancing or in case of primary server downtime)
g	GIF file
I	Image file
T	Telnet 3270

And thats it, the whole protocol.