Cannot catch listen() addressinuse error….

4 thoughts on “Cannot catch listen() addressinuse error….”

1. Just wondering, why do you want to catch it? Isn’t better if you “let it go”

2. What version of Node.js are you using? With Express 4.13.3 on Node.js 0.12.1, I found your second option worked for me.

   Simple test

   var express = require('express');
   var http = require('http');
   var app = express();
   
   http.createServer(function(req, res) {}).on('error', console.log).listen(3000);
   
   // These should all print the error object to console
   http.createServer(function(req, res) {}).on('error', console.log).listen(3000);
   http.createServer(function(req, res) {}).listen(3000).on('error', console.log);
   app.listen(3000).on('error', console.log);

   Output I get

   node test.js
   { [Error: listen EADDRINUSE] code: 'EADDRINUSE', errno: 'EADDRINUSE', syscall: 'listen' }
   { [Error: listen EADDRINUSE] code: 'EADDRINUSE', errno: 'EADDRINUSE', syscall: 'listen' }
   { [Error: listen EADDRINUSE] code: 'EADDRINUSE', errno: 'EADDRINUSE', syscall: 'listen' }
   
   

3. The Server object is a Node.js EventEmitter. As with all EventEmitter’s, most errors are passed to the 'error' event. If no handler is registered for the 'error' event, those bubble up to be thrown. try/catch does not work because when listen is attempted, any errors that occur are caught and emitted on the 'error' event using process.nextTick() — that is, by the time the error is actually reported, the try/catch block has already exited. As a fallback, you can register an 'uncaughtException' handler on process as a catch all for any unhandled errors that occur on any EventEmitter object, but it’s best to simply set the 'error' callback on the server object. @tunniclm‘s example ought to work for you.

4. The “proper” way to do this is:

   var express = require('express');
   var http = require('http');
   var app = express();
   var server = http.createServer(app);
   server.on('error', function (e) {
     // do your thing
   });
   server.listen(3000);

   Make the server yourself and bind the event before you start listening.

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