EN Bridge Connector Telnet

Telnet connector

Français · How-to + reference · Published, reviewed by a person · Applies from: 4.2.5

The Telnet connector opens a small virtual terminal on a TCP port: a player connects, types the pairing code their game shows, then the commands the game declares (lamp on), and each declared command proposes its signal. Nothing typed is ever run: there is no shell behind it. It is experimental, like every connector (Connectors overview).

Audience, context, and the statuses of what this page rests on

Audience: admin · Context: Reality Bridge

The connectors (email, Telnet, SSH, Open Badges) · contract: experimental · verified by CI (support matrix of 4.4.0, 2026-10-23): Node 22 on Ubuntu (Telnet and SSH not on Windows) · automated checks: jobs connectors, connector-archive-e2e; CI plan reality; 3 test files · people's passes: connectors-real-security not run (#79) · known limits: bridge-telnet-clear-text

What you get

A quest-n-click-connector telnet process listening on a port, printing the game's banner and prompt, answering the commands of reality.connectors.telnet, and proposing their signals for the player who linked the session.

Context and versions

• A connector beside a running Bridge, from 4.1.9; this page applies from 4.2.5 (the quest-n-click-connector name).
• Verified on: the steps were run on 23 October 2026 against a local Bridge of the game signals (macOS, Node 22.14, engine 4.4.0, nc as the client): the banner, Linked. Resume word, for 30 minutes: R…, then lamp on answered "Click. Somewhere in the garden, a lamp glows." and accepted by the Bridge.

Limit · bridge-telnet-clear-text Telnet is clear text: the pairing code and every line cross the network as typed. Keep it on a local network, behind a VPN or TLS (stunnel), or prefer SSH.

Prerequisites

• A running Bridge (Install and run the Bridge) and a game whose reality.connectors.telnet declares its commands (Signals and the manifest):

  telnet: { banner: 'GARDEN SHED TERMINAL.', prompt: 'shed> ', commands: [{ says: 'lamp on', reply: 'Click.', signal: 'terminal.lamp' }] }

Where to run the commands

grant where the Bridge's folder is; the connector on the machine players connect to, in a folder holding its configuration and token. npm run connector -- telnet … in the engine repository, npx quest-n-click-connector telnet … with the package.

Steps

1. Grant the connector its token, for the terminal's signals only, with pairing:

   # in the engine repository (the Bridge's folder is .cache/bridge)
   npm run bridge -- grant --connector=shed-telnet --source=terminal --signals=terminal.lamp --pair > telnet.token

2. Write its configuration, telnet.json:

   {
     "bridge": { "url": "http://127.0.0.1:8787/", "tokenFile": "telnet.token" },
     "gameId": "signals",
     "limits": { "maxBytes": 4096, "maxPerMinute": 60, "timeoutMs": 5000 },
     "health": { "port": 9301 },
     "telnet": { "port": 2323 }
   }

3. Start it:

   # in the engine repository
   npm run connector -- telnet --config telnet.json

   It logs {"event":"telnet.started","connector":"telnet","port":2323}.

4. Connect as a player would, type the code the game shows, then a declared command:

   # on a machine that reaches the port
   nc 127.0.0.1 2323

   The terminal prints the banner, asks for the pairing code, answers Linked. Resume word, for 30 minutes: RABCD-EFGH, then Type help to see what this terminal knows. and the prompt. lamp on prints the command's reply and proposes terminal.lamp.

Expected result, and how to check it

• GET http://127.0.0.1:9301/health answers 200 {"connector":"telnet","ok":true,"detail":"<n> session(s) on port 2323",…}; GET /metrics gives proposed, accepted, duplicates, refused, rejectedInputs, retries.
• The Bridge logs "event":"pairing.confirmed", then "event":"signal.accepted" with terminal.lamp.

Common errors

What the terminal says	Cause	Fix
That code does not work. Try again., then Too many wrong codes. Goodbye.	A wrong or expired code, three times on one connection	A new code from the game's World link
The connection is refused at once	Six wrong codes from that address in ten minutes, across reconnections; or 3 connections already open from it, or 20 in all	Wait; close idle sessions
Unknown command. Type help.	Not a declared command (matched whole, lower case)	help lists them
(the world did not answer: <code>)	The Bridge refused the proposal (denied, player, bridge-quota, unreachable…)	Read the connector's and the Bridge's logs
The connection closes after a minute	No complete line for a minute, or not linked within 20 seconds	Type the code at once
Slow down. / Line too long (512 bytes at most).	Over 100 lines a minute / a line over 512 bytes	Type less, shorter

Files or data changed

None on disk. Resume words live in memory for 30 minutes; nothing typed is stored.

Recovery or going back

Stop the process (SIGTERM: it reads nothing more, drains, exits 0). If its token leaked, revoke it on the Bridge (revoke --token=<revocation id>) and grant a new one.

Reference: what the terminal does

• telnet: { "port": 2323, "host": "127.0.0.1", "limits": { … } }: host defaults to 127.0.0.1; limits overrides the terminal's limits below, by name.
• A TCP server that refuses every Telnet option and filters the protocol's bytes.
• The player types the pairing code (or the resume word printed at a previous pairing), then the commands the game declares. help, clear and exit (or quit) are the terminal's own.
• Each line typed is a new fact: its key is sha256('telnet:' + session + ':' + line number). A command typed twice proposes its signal twice; the game's once decides whether it acts twice.

Limit (limits name)	Default
A line (maxLine)	512 bytes; a longer one is refused whole, Line too long (512 bytes at most).
Lines (linesPerMinute)	100 a minute; beyond, Slow down. and the line is dropped
Input (bytesPerSecond)	64 KB a second received; beyond, the connection is closed
Time to link (pairMs)	20 seconds
Time between lines (idleMs)	1 minute
A session (sessionMs)	30 minutes
Connections per address (perAddress) / in all (maxConnections)	3 / 20
Wrong codes per address (triesPerAddress in triesWindowMs)	6 in 10 minutes, across reconnections

Guarantee · bridge-telnet-address-limits · referenced · executed on 47dccf1b4b15 · scope reviewed One address holds three connections at most, and its wrong codes are counted across reconnections; an unlinked connection is closed.

What it keeps

Nothing typed is stored: a line is matched against the game's commands and forgotten; the Bridge receives only the signal's name. A resume word links a later session to the same player for 30 minutes, in memory. The client's address is used by the operating system for the connection, and counted in memory for the limits; the connector keeps no list of them.

References

• The code: connectors/src/telnet/connector.ts, connectors/src/terminal/ (limits, lines, the virtual shell).
• The threat model: docs/dev/threat-models/telnet.md.
• Tested by tests/connectors-terminal.test.ts: floods, slow clients, a thousand connections.

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