socket-application

socket-application is a cursor rule for Cursor from AxiosLeo/node-koapp. It costs 952 tokens per session, scanned A, original, MIT.

Guidance for building TCP socket and WebSocket servers with the Koapp Node.js framework. It explains how these server types relate and share connection-management methods.

In plain words
What is it for?
Use it when setting up socket or WebSocket applications, routing messages, sending data to a connection, closing connections, retrieving connections, or sending ping messages.
Why use it?
It prevents confusion about which application class to use and where connection operations are defined. It also clarifies the message format expected by TCP socket clients.

Cursor rule for Cursor

Written for Cursor: a Cursor rule (.mdc). Also seen: installed under .agents/ (shared by several agents).

Good fit Use it when setting up socket or WebSocket applications, routing messages, sending data to a connection, closing connections, retrieving connections, or sending ping messages.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/axiosleo/node-koapp/socket-application
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/AxiosLeo/node-koapp

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for socket-application

README.md
[![agentmods](https://agentmods.dev/badge/rules/axiosleo/node-koapp/socket-application/github.svg)](https://agentmods.dev/rules/axiosleo/node-koapp/socket-application)
Your own site
<a href="https://agentmods.dev/rules/axiosleo/node-koapp/socket-application"><img src="https://agentmods.dev/badge/rules/axiosleo/node-koapp/socket-application/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for socket-application

Your own site · 80×15
<a href="https://agentmods.dev/rules/axiosleo/node-koapp/socket-application"><img src="https://agentmods.dev/badge/rules/axiosleo/node-koapp/socket-application.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 952 This file is loaded in full into every session.
When invoked 952 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00952 $0.00952
Opus 5.5 $0.00381 $0.00381
Sonnet 5.5 $0.00190 $0.00190
Haiku 4.5 $0.00095 $0.00095

Measured today against content hash 5f6aedef32ea, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

socket-application scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/rules/socket-application.mdc · 127 lines

How it starts

The opening of the file, as written. The whole thing — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Socket Application Patterns

Class Hierarchy

Application (base)
  └── SocketApplication (TCP socket, extends Application)
        └── WebSocketApplication (WebSocket, extends SocketApplication)

WebSocketApplication extends SocketApplication, not Application directly. Connection management methods (sendByConnectionId, closeByConnectionId, getConnection, ping) are defined once in SocketApplication and inherited by WebSocketApplication.

SocketApplication Setup

TCP socket server using net.createServer:

const { SocketApplication, Router } = require("@axiosleo/koapp");

const router = new Router("/", { /* ... */ });

const app = new SocketApplication({
  routers: [router],
  port: 8801,
  ping: {
    open: true,
    interval: 1000 * 10,
    data: "this is a ping message",
  },
});

app.start();

Message protocol: JSON payload terminated by @@@@@@ delimiter.

{"path":"/test","method":"GET","query":{"test":123}}@@@@@@

WebSocketApplication Setup

WebSocket server using the ws library:

const { WebSocketApplication, Router } = require("@axiosleo/koapp");

const router = new Router("/", { /* ... */ });

const app = new WebSocketApplication({
  routers: [router],
  port: 8801,
  ping: {
    open: false,
    interval: 1000 * 3,
    data: "this is a ping message",
  },
});

app.start();

Message protocol: plain JSON string (no delimiter).

{"path":"/test","method":"GET","query":{"test":123}}

Ping Configuration

Both applications support automatic heartbeat via pingConfig:

Field Type Default Description
open boolean false Enable periodic ping
interval number 300000 (5min) Milliseconds between pings
data any "this is a ping message" Payload sent with each ping

Read the full file on GitHub · 127 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. today Changed 5f6aedef32ea
  2. 1mo ago First seen · 127 lines · 952 tokens per session scan A 12283fddd5ad

Subscribe to this mod's changes

socket-application is a cursor rule published in the GitHub repository AxiosLeo/node-koapp (143 stars, last pushed yesterday), licensed MIT. It adds 952 tokens to every session, about $0.0038 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.