node-portfinder
Installation
You can install portfinder using a package manager like npm, yarn, or bun:
npm install portfinder
Usage
The portfinder module has a simple interface:
const portfinder = require('portfinder');
portfinder.getPort(function (err, port) {
  //
  // `port` is guaranteed to be a free port
  // in this scope.
  //
});
Or using promises:
const portfinder = require('portfinder');
portfinder.getPortPromise()
  .then((port) => {
    //
    // `port` is guaranteed to be a free port
    // in this scope.
    //
  })
  .catch((err) => {
    //
    // Could not get a free port, `err` contains the reason.
    //
  });
Ports search scope
By default portfinder will start searching from 8000 and scan until maximum port number (65535) is reached.
You can change this globally by setting:
portfinder.setBasePort(3000);    // default: 8000
portfinder.setHighestPort(3333); // default: 65535
or by passing optional options object on each invocation:
portfinder.getPort({
  port: 3000,    // minimum port
  stopPort: 3333 // maximum port
}, callback);
Run Tests
npm test