port-authority

Utilities for dealing with ports in Node apps.

!Port Authority

``js
import * as ports from 'port-authority';

async function start(port) {
if (port) {
// if the selected port is unavailable,
// print something nicer than EADDRINUSE
const available = await ports.check(port);
if (!available) {
console.log(> Port ${port} is unavailable);
return;
}
} else {
// if no port was selected, start at 3000
// and keep counting until we find one
port = await ports.find(3000);
}

const proc = child_process.fork('server.js', [], {
env: {
PORT: port
}
});

try {
await ports.waitUntilBusy(port, {
timeout: 5000
});

console.log(> Server is running on port ${port});

setTimeout(() => proc.kill(), 100);
await ports.waitUntilFree(port);

console.log(> Port ${port} is free);
} catch (err) {
console.log(> Could not find server on port ${port});
proc.kill();
}
}

start();
`

There are existing libraries to do this stuff, but I couldn't find any that do all the things that port-authority does, with treeshakeable functions and a modern Promise-based API.

Additional functions

On Unix-like systems, you can also do the following:

`js
// Find the process ID that is using port n.
// Returns null if port is currently unused
const pid = await ports.blame(n);

// Kill the process using port n, if any.
// Returns true if the port was in use
const killed = await ports.kill(n);
``

PRs welcome to make this work on all operating systems.

License

LIL