javascript - How can I check if port is busy in NodeJS?

Question

How can I check if port is busy for localhost?

Is there any standard algorithm? I am thinking at making a http request to that url and check if response status code is not 404.

Answer 1

You could attempt to start a server, either TCP or HTTP, it doesn't matter. Then you could try to start listening on a port, and if it fails, check if the error code is EADDRINUSE.

var net = require('net');
var server = net.createServer();

server.once('error', function(err) {
  if (err.code === 'EADDRINUSE') {
    // port is currently in use
  }
});

server.once('listening', function() {
  // close the server if listening doesn't fail
  server.close();
});

server.listen(/* put the port to check here */);

With the single-use event handlers, you could wrap this into an asynchronous check function.