Common Text-based Response Protocol

Common Text-based Response Protocol
Developer	secondtruthLabs
Status	Stable
First published	2025
Latest version	1.0
Transport	TCP
Encoding	UTF-8
License	Public Domain

The Common Text-based Response Protocol (CTRP) is a foundation protocol for building lightweight, text-based application protocols over TCP. Developed by secondtruthLabs, it defines common conventions for simple request-response communication patterns.

Overview

CTRP serves as a base layer upon which application-specific protocols can be built. Rather than defining a complete application protocol itself, CTRP establishes conventions for message formatting, status codes, and connection handling that derived protocols inherit and extend.

Design philosophy

CTRP follows a minimalist approach inspired by classic internet protocols like Finger and Gopher. Key principles include:

• Simple enough to implement in a weekend
• Consistent patterns across derived protocols
• Optimized for text content delivery
• Minimal overhead

Technical specification

Request format

Requests consist of a single line terminated by CRLF (\r\n):

Basic request format

{{{code}}}

The maximum request line length is 1024 bytes.

Response format

Responses begin with a status line, followed by optional content:

Response format

{{{code}}}

Content is terminated by a line containing only a period (.).

Status codes

CTRP uses a hierarchical status code system:

Range	Category	Description
1x	Informational	Request received, continuing process
2x	Success	Request successfully processed
3x	Redirection	Further action needed
4x	Client Error	Request contains bad syntax or cannot be fulfilled
5x	Server Error	Server failed to fulfill valid request
6x	Service Error	Service-level issues

Common status codes:

Code	Message	Meaning
20	OK	Success
21	OK+MORE	Success, more content available
40	BAD REQUEST	Malformed request
41	NOT FOUND	Requested resource not found
42	FORBIDDEN	Access denied
50	ERROR	General server error
51	NOT IMPLEMENTED	Command not supported

Encoding

All CTRP communication uses UTF-8 encoding with CRLF line endings. This ensures consistent handling across platforms while supporting international character sets.

Transport security

CTRP supports optional TLS encryption. Implementations typically offer both plain TCP and TLS-secured connections on separate ports.

Derived protocols

The following protocols are built on CTRP:

• AgentFinger – AI agent discovery and information

See also

• AgentFinger
• Trivial Service Discovery Protocol
• wp:Finger protocol
• wp:Gopher (protocol)

External links

• CTRP Specification Repository