In A Storm

Finds a port to bind your server to. 'In A Storm' is inspired by (and some code has been taken from) find-and-bind, but gives you more ways of specifying what port(s) you want, and uses promises rather than node style callbacks.

$ npm install in-a-storm

Usage

'In A Storm' provides a listen function that is designed to work with any server that exposes the same interface as the node net.Server class. It returns a promise that will be fulfilled with the port number it is listening on.

var listen = require('in-a-storm');

listen(app).then(function(port) {
	console.log('Listening on port', port);
});

// or....

listen(app).then(function(port) {
	console.log('Listening on port', port);
}).catch(function(err) {
	console.error('Something weird happened and I was unable to bind to any port at all : ' + err);
});

It will select an unused port, and bind your app to it.

If your app is an instance of http.Server, it will try the port in the environment variable PORT first, then it will try port 80, then it will try port 8080 before trying a port at random.

If your app is an instance of https.Server, it will try 443, then 8443 before a random port.

Specifying the ports to use

There are a number of ways to specify preferences for ports to use.

// try port 8080, if that fails, select a random port.
listen(server, 8080);
listen(server, "8080");

// try port 8080, then 8081, then 8082, then if that fails, select a random port.
listen(server, "8080-8082");

// try port 80, then port 8080, then port 1000, then port 1001, then 1002, then a random port.
listen(server, [80, 8080, "1000-1002"]);

// bind to a specific host address 'myhost' with backlog.
listen(server, [80, 8080, "1000-1002"], 'myhost', backlog);

Compatible Servers

All servers that behave like net.Server will work.

To work correctly, the listen functions first argument must be the port to bind to and it must emit a 'listening' event when the port is successfully bound. It should also emit an error event if the port cannot be bound. If the port is set to 0, then a random available port must be chosen. In order for in-a-storm to find out which port has been chosen, the server must provide a .address() method providing a result with the port on it.

If you call the listen function with a function instead of a server object, it is assumed that this is an http handler like an express app, and an http server is created for it.

Future Work

The tests are mainly just modified versions of what find-and-bind does, so more work is needed there.

There might well be other sensible default behaviours that can be added based on the instance of the server.