LetsExchange WebSocket Listener

A reliable backend service that eternally listens to the LetsExchange Fiat API WebSocket and stores every incoming message into a MongoDB collection.

This service is designed for long-running production environments, ensuring that any WebSocket disconnect or error triggers an immediate automatic reconnection.

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🔧 Features

• Eternal WebSocket Listener
  Automatically listens to the LetsExchange transaction feed at:
  =wss://fiat-api.letsexchange.io/transaction/?EIO=3&transport=websocket

• Automatic Reconnection
  Instantly reconnects when:

  • The WebSocket drops
  • A network error occurs
  • A timeout or server disconnect happens

• MongoDB Storage
  Stores every message in a configurable MongoDB collection.

• Fully Configurable
  MongoDB URI, delays, log level, WebSocket URL, etc., are set via .env.

• Graceful Shutdown
  Cleanly closes WebSocket and DB connections.

• Docker Support
  Run the entire service inside a container.

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📁 Project Structure

letsexchange-ws-listener/
├─ src/
│  ├─ index.js               # Entry point
│  ├─ config.js              # Loads & validates environment variables
│  ├─ logger.js              # Logging utility
│  ├─ mongo.js               # MongoDB connection helper
│  ├─ websocketClient.js     # WebSocket connection + reconnection logic
│  └─ messageHandler.js      # Processes & stores messages
│
├─ .env.example              # Example environment variables
├─ .gitignore                # Ignore rules
├─ Dockerfile                # Docker support
├─ package.json              # Dependencies & scripts
├─ package-lock.json         # Auto-generated lock file
└─ README.md                 # Documentation


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🚀 Setup Instructions

1. Clone the Repository

git clone https://github.com/Arsenic-23/exchangeservice.git
cd exchangeservice

2. Install Dependencies

npm install

3. Create Your .env File

cp .env.example .env

Fill .env with:

WS_URL==wss://fiat-api.letsexchange.io/transaction/?EIO=3&transport=websocket

MONGODB_URI=mongodb://localhost:27017
MONGODB_DB_NAME=exchangeservice
MONGODB_COLLECTION=transactions

RECONNECT_DELAY_MS=5000
MAX_RECONNECT_DELAY_MS=60000

LOG_LEVEL=info


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▶️ Run the Service

npm start

Expected output:

> letsexchange-ws-listener@1.0.2 start
> node src/index.js

{"level":"info","timestamp":"2025-11-22T16:38:30.477Z","message":"Starting LetsExchange WebSocket Listener Service..."}
{"level":"info","timestamp":"2025-11-22T16:38:30.479Z","message":"Connecting to MongoDB..."}
{"level":"info","timestamp":"2025-11-22T16:38:32.033Z","message":"MongoDB connection established."}
{"level":"info","timestamp":"2025-11-22T16:38:32.307Z","message":"MongoDB indexes ensured."}
{"level":"info","timestamp":"2025-11-22T16:38:32.308Z","message":"Connecting to Socket.IO","meta":{"url":"wss://fiat-api.letsexchange.io/transaction/?EIO=3&transport=websocket"}}
{"level":"info","timestamp":"2025-11-22T16:38:32.315Z","message":"Service running."}
{"level":"info","timestamp":"2025-11-22T16:38:35.392Z","message":"Socket.IO connected"}
{"level":"info","timestamp":"2025-11-22T16:38:35.393Z","message":"Subscription frame sent","meta":{"frame":"42[\"subscribe\",\"transaction\"]"}}
{"level":"info","timestamp":"2025-11-22T16:38:30.477Z","message":"Starting LetsExchange WebSocket Listener Service..."}
{"level":"info","timestamp":"2025-11-22T16:38:30.479Z","message":"Connecting to MongoDB..."}
{"level":"info","timestamp":"2025-11-22T16:38:32.033Z","message":"MongoDB connection established."}
{"level":"info","timestamp":"2025-11-22T16:38:32.307Z","message":"MongoDB indexes ensured."}
{"