[spec] ☿️ gemini — a minimalist gemini protocol

Petite Abeille petite.abeille at gmail.com
Tue Mar 2 11:58:08 GMT 2021

All details are similar to gemini itself, ± some minor adjustments.



By default, a ☿️ gemini service runs over plain TCP, at port 1961.

A ☿️ gemini:// request is one-line —4,096 bytes long at most, UTF-8 encoded— containing a fully qualified, normalized Internationalized Resource Identifier (IRI):


An IRI is an UTF-8 version of an Uniform Resource Identifier (URI). 
An URI can be either an Uniform Resource Locator (URL), or Uniform Resource Name (URN).


An example of a ☿️ gemini request, followed by a ☿️ text/gemini response:

# echo -e 'gemini://gemini.xyz:1961/\r\n' | nc 1961
20 text/gemini;charset=utf-8;
Hello ☿️ Gemini!

=> gemini://host.xyz:1961/license CC0-1.0 
<end of connection> 

A successful ☿️ gemini response is a one-line with status 20—optionally followed by a content type, plus associated attributes, such as encoding:  

20 text/gemini;charset=utf-8;

The content type is optional — defaulting to ☿️ text/gemini, UTF-8 encoded.

The content itself follow the  20 status line — terminated by the service dropping the network connection.


There are 3 status codes:

20 SUCCESS — one-line, with optional content type, plus attributes, 4,096 bytes long at most, UTF-8 encoded
20 text/gemini;charset=utf-8;

30 REDIRECT — one-line IRI, fully qualified, and normalized, 4,096 bytes long at most, UTF-8 encoded
30 gemini://host.xyz:1961/

40 ERROR — one-line, 4,096 bytes long at most, UTF-8 encoded, with optional description 
40 ⚠︎☿️⚠︎


A ☿️ text/gemini consists of two line types: text, and link. 

A link is denoted as one-line, starting with the arrow symbol (=>), followed by a space, followed by a fully qualified, and normalized IRI — optionally followed by a space separated description:

=> gemini://host.xyz/license CC0-1.0

All other lines are regular text lines.


That's all folks.


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