---
id: telnetlib3
version: "5.0.0"
license: ISC
license_treatment: permissive
maintenance: active
---

# telnetlib3 — Python Telnet server and client CLI and Protocol library

License: permissive · Maintenance: active · Downloads: 1.7M/mo

## What it is and what it does

Telnetlib3 is a feature-rich Telnet implementation that provides both asyncio-based and synchronous blocking APIs for building telnet servers and clients. It implements RFC specifications for telnet protocol negotiation, including support for binary transmission, character encoding negotiation, compression (MCCP2/MCCP3), terminal type detection, and window size reporting. The library includes command-line utilities (telnetlib3-client, telnetlib3-server) for quick telnet connections and hosting, plus fingerprinting tools. For Python 3.13+, it provides a drop-in shim for the removed standard telnetlib module, allowing existing code to continue working unchanged.

The package is designed for developers building MUD (Multi-User Dungeon) and BBS (Bulletin Board System) servers, retro computing applications, and other telnet-based systems. It handles encoding negotiation automatically when possible, supports raw mode for non-compliant servers, and can host external programs via pseudo-terminal (PTY) execution. Dependencies are minimal (blessed for terminal handling, wcwidth for character width calculation), and the codebase is actively maintained with broad Python version support.

Use it for:

- Build a telnet server for a MUD or interactive game with custom shell logic and protocol negotiation
- Connect to legacy BBS systems or telnet servers with automatic or manual encoding handling (cp437, big5bbs, ATASCII)
- Host a CLI/TUI program (e.g., bash, bc) as a telnet service with optional linemode or raw mode
- Migrate Python 3.13+ code that relied on the standard telnetlib module by installing telnetlib3 as a drop-in replacement
- Implement telnet client automation scripts that negotiate compression and terminal capabilities with remote servers
- Fingerprint telnet servers to detect their capabilities and protocol support

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Telnet server, client, and protocol library for Python 3.9+ with asyncio and blocking API support, including CLI utilities and a backport of the removed telnetlib module for Python 3.13+.

Yes. The package is actively maintained, has no known vulnerabilities, low install friction, and a permissive license. It fills a genuine gap left by the removal of telnetlib in Python 3.13 and provides a modern, well-specified implementation for telnet server/client work. Install it if you need telnet support, are migrating from the standard library, or are building MUD/BBS infrastructure.

## Install

pip install telnetlib3
uv add telnetlib3
poetry add telnetlib3

## Installing telnetlib3

Before you install: Low friction: pure Python wheel with only two runtime dependencies (blessed, wcwidth). Actively maintained with a release 7 days ago. Supports Python 3.9 through 3.14.

License in practice: ISC license is permissive and poses no restrictions on use, modification, or distribution in commercial or private projects.

Quickstart:

import asyncio
import telnetlib3

async def shell(reader, writer):
    writer.write('Hello\r\n')
    await writer.drain()
    writer.close()

async def main():
    server = await telnetlib3.create_server(port=6023, shell=shell)
    await server.wait_closed()

asyncio.run(main())

Requires Python 3.9 or newer; asyncio event loop required for async API.

Verify before relying:

- Whether the blocking API is feature-complete relative to the asyncio interface
- Performance characteristics under high concurrency or large message volumes
- Compatibility with non-standard telnet implementations beyond the RFC specifications listed

## Package facts

- License: ISC (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 1.7M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

telnet server client library, asyncio telnet protocol, telnet CLI utilities, python telnet implementation, MUD BBS telnet support, telnet with compression MCCP, telnet character encoding negotiation, telnet-protocol, asyncio-ready, retro-computing

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