Ubuntu VM port is enabled but not working

Gurpal Singh 1

I added port 448 on VM networking inbound security rules. it is also added on OS level like
ufw allow 448/tcp. it shows

Rules updated  
Rules updated (v6).

But when i am trying to access on browser it shows ERR_CONNECTION_REFUSED. also not showing in open port list.
list of all opened port on azure side

list of all opened port on ubuntu VM

Also OS level firewall is showing inactive

3 answers

msrini-MSFT 9,261 Reputation points Microsoft Employee

2023-01-10T06:36:45.793+00:00
Hi,

The flow is as mentioned below:

You will need to allow port 448 on NSG - subnet level/NIC level.

Port 448 needs to be listening on your guest OS.

You need to check if this port is being blocked by IP tables.

If you have verified the above, you will need to perform a packet capture on your VM and see if you are able to see the packet on the VM. By doing that you can understand if the connection reset is from application or from OS.

Regards, Karthik Srinivas
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1 person found this answer helpful.
Gurpal Singh 1 Reputation point

2023-01-10T11:59:29.197+00:00

I checked 448 is allow on NSG and there is no subnet. Screenshot attached below

Port 448 is not listening on OS. This is the issue i am facing. i am adding it like sudo ufw 448/tcp. i shows allowed but when i am checking list of all opened port it is not there.

How i can check IP tables?

Temuujin Yavuuzandan 0 Reputation points

2023-06-04T17:57:21.1033333+00:00

Port 448 needs to be listening on your guest OS.

was the point. I faced some problem but after allowing 8080 in nsg and starting my applica with 8080 it works fine. Attention to your host url, don't start your application with localhost:8080, just :8080 will work.
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Manu Philip 16,986 Reputation points MVP

2023-01-09T13:22:08.077+00:00

As you have confirmed the port is opened, try running an application listening at port 448 and then check out using nmap localhost. See the port is listening and under the list

--please don't forget to upvote and Accept as answer if the reply is helpful--
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Gurpal Singh 1 Reputation point

2023-01-09T14:02:36.793+00:00

Starting Nmap 7.60 ( https://nmap.org ) at 2023-01-09 14:01 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00063s latency).
Not shown: 996 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
443/tcp open https
3306/tcp open mysql

my port not showing here

Manu Philip 16,986 Reputation points MVP

2023-01-09T19:55:23.843+00:00

Looks like, you haven't run an application listening the required port yet. Following commands will help
nc -l 448

Now check if the port is able to find in the listening ports list

Gurpal Singh 1 Reputation point

2023-01-10T04:24:30.753+00:00

Port is listening for sometime, when i am checking after one minute it is disappearing. You can see below screenshot, port shows but i checked again it is disappear and showing ERR_CONNECTION_REFUSED

Gurpal Singh 1 Reputation point

2023-01-10T05:11:31.97+00:00

sudo ufw verbose Status: active

To Action From

448/tcp ALLOW Anywhere
448 ALLOW Anywhere
448/tcp (v6) ALLOW Anywhere (v6)
448 (v6) ALLOW Anywhere (v6)
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msrini-MSFT 9,261 Reputation points Microsoft Employee

2023-01-10T12:12:55.763+00:00

Ok. This looks like your application is not listening on the port. Which application are you using ?

Can you access your application locally?
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Gurpal Singh 1 Reputation point

2023-01-10T12:34:20.263+00:00

i can access application local server. But when i am trying with. something like https://sitename.com:448 for nodejs

its not working

Gurpal Singh 1 Reputation point

2023-01-11T05:25:20.01+00:00

It is on ubuntu VM and apache is installed, working on port 443, now i want to work nodejs on same server with port 448
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