NMEAFlow: Sensor Server Simulator

NMEAFlow is a basic CLI tool designed to emulate a sensor server, which can broadcast data from one or more simulated sensors at the same time. The data is read from text files and replayed continuously, at desired intervals.

Use NMEAFlow for developing and testing applications that consume real-time sensor data, without the need for actual sensors.

Features

• Replay any data from text files
• Flexible port configuration
• Extensive logging and error handling
• Dynamic interval settings
• Pre-loaded with sample NMEA strings for various marine sensors
• Types included for TypeScript support
• Programmatic API for further integration

Requirements

• Node.js >= v14.x
• NPM >= v6.x

Installation

npm install nmeaflow

Command Line Usage

Options

Option	Description	Default Value
--port-start	Starting port for the simulator	4001
--port-end	Ending port for the simulator	4006
-c, --config	Config file with list of files to replay
--id	Id for an individual simulator instance
-p, --port	Single port to run an individual simulator instance
-f, --filename	Filename for an individual simulator instance
-i, --interval	Broadcasting interval for an individual simulator instance in milliseconds	10000
-a, --address	Address to listen on	localhost
-h, --host	Listen to all available IPs
--log-level	Specify log level	debug

Logging

You can set the log level either by running using the --log-level option or by setting the LOG_LEVEL environment variable.

The log levels are as follows:

• error
• warn
• info
• verbose
• debug
• silly
• none

Config File

The config file is a JavaScript file that exports an array of objects. Each object contains the file, id, and interval keys.

Example:

module.exports = [
  { file: 'gps.txt', id: 'GPS', interval: 10000 },
  { file: 'trawl.txt', id: 'TRAWL_SONAR', interval: 15000 },
  { file: 'depthsounder.txt', id: 'DEPTH_SOUNDER', interval: 15000 },
  { file: 'wind.txt', id: 'WIND', interval: 10000 },
];

The interval can be either a number (in milliseconds) or a function. The function takes the id as argument and should return a number representing the interval in milliseconds.

Running as an individual instance

To run the simulator as an individual instance you need to specify the individual parameters, as follows:

nmeaflow -p 4000 -f sample_data.txt -id Sensor01 --interval 10000

This will run the simulator with id Sensor01 on port 4000, reading data from the file sample_data.txt, and broadcasting the data every 10,000 milliseconds (or 10 seconds).

Programmatic API

NMEAFlow comes with type definitions, enabling easy integration into TypeScript projects. Here's an example:

import { NMEAFlow } from 'nmeaflow';

const options = {
  address: 'localhost',
  port: 4001,
  filename: 'custom_data.txt',
  interval: 2000,
};

const simulator = new NMEAFlow(options);
simulator.start()
  .then(() => {
    console.log('Simulator started');
  })
  .catch((err) => {
    console.error('Failed to start simulator', err);
  });

License

MIT