无法运行简单的node.js应用抛出错误：监听EACCES

Question

I ussually code on c9 I am trying to get work on my local environment, Im a trying a ver silly app but I get an error.

APP:

//APP IMPORTS
var express    = require('express'),
    app        = express()


//INDEX PAGE
app.get('/', function(req, res) {
   res.send('Welcome');
});


app.listen('localhost', 30000, function() {
   console.log("mirror server started!"); 
});

Error:

λ node app.js
events.js:167
      throw er; // Unhandled 'error' event
      ^

Error: listen EACCES localhost
    at Server.setupListenHandle [as _listen2] (net.js:1269:19)
    at listenInCluster (net.js:1334:12)
    at Server.listen (net.js:1432:5)
    at Function.listen (c:\Moi\mirror\node_modules\express\lib\application.js:618:24)
    at Object.<anonymous> (c:\Moi\mirror\app.js:12:5)
    at Module._compile (internal/modules/cjs/loader.js:688:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:699:10)
    at Module.load (internal/modules/cjs/loader.js:598:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:537:12)
    at Function.Module._load (internal/modules/cjs/loader.js:529:3)
Emitted 'error' event at:
    at emitErrorNT (net.js:1313:8)
    at process._tickCallback (internal/process/next_tick.js:63:19)
    at Function.Module.runMain (internal/modules/cjs/loader.js:744:11)
    at startup (internal/bootstrap/node.js:285:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)

Not sure why this is happening I was trying first with process.env.IP and process.env.PORT but I didnt want to set the environment vars yet, and I dont know what ip node uses for default, so I tried like thisnot sure why it doesnt work, I also tried with an ip like '127.0.0.22' and PORT 3000, etc.

Answer 1

You have the port number and "bind host" in the wrong order. It should be:

app.listen(30000, 'localhost', ...)

Answer 2

Try following to get your app started:

//APP IMPORTS
var express    = require('express'),
    app        = express()


//INDEX PAGE
app.get('/', function(req, res) {
   res.send('Welcome');
});

app.set('port', 30000);

app.listen(app.get('port'), function() {
   console.log("mirror server started!"); 
});

Your server should automaticaly get localhost as host and change as soon as you work on production with your server host.

Another way

Just replace the order of your listen function parameter like:

app.listen(30000, 'localhost',  function() {
   console.log("mirror server started!"); 
});

The signature like express described looks like this: app.listen([port[, host[, backlog]]][, callback])

Source: Express documentation
You can find here a small explanation on how express handelt server config