How Can I Open A Port On Ubuntu?

Question

Ubuntu 13.04:

No LSB modules are available
Distributor ID: Ubuntu
Description:    Ubuntu 13.04
Release:        13.04
Codename:       raring

I'm attempting to open port 8888 on an Ubuntu VM that I'm accessing with VirtualBox/Vagrant. On the vm, I run the following command

vagrant@vagrant-ubuntu-raring-32:~$ curl -v 'http://localhost:8888'

and I get the following response:

* About to connect() to localhost port 8888 (#0)
*   Trying 127.0.0.1...
* Connection refused
* Failed connect to localhost:8888; Connection refused
* Closing connection 0
curl: (7) Failed connect to localhost:8888; Connection refused

So I then try this (per an answer I found here on AskUbuntu):

sudo ufw allow 8888/tcp

Then I retry the curl command and I get the same thing. Not that it should make any difference but I sudo the curl command and it makes no difference. I've also reverted the machine to baseline and then run sudo ufw allow 8888 and that doesn't work either. Are there other things which might be blocking that port?

Answer 1

Is anything listening on port 8888? If nothing is listening on the port you can't connect to it.

You can check if anything is listening on that port with

sudo netstat -tulpn

The port is likely open already as linux firewalls won't block localhost if you don't ask them to block it.