Challenge ·Easy

Find the Listening Port

Sherif Asker
by  Sherif Asker · on
NetworkingLinux
A mystery service is running on this VM. Find which TCP port it is listening on and write the port number to /tmp/answer.
#internship#ports

A mystery service is running on this Linux VM. Your job is to discover which TCP port it is listening on, and then write that port number (just the number, no extra characters) to /tmp/answer.

Hint 1 — what tool should I use?

ss (socket statistics) is the modern replacement for netstat. Try ss -tnlp to list tcp sockets in listen state, with numeric addresses and process info.

Hint 2 — how do I write the answer?

Once you know the port number N:

echo N > /tmp/answer

Then click "Verify" again.

How to Author Challenges on iximiuz Labs

Instead of providing a subpar online editing experience, iximiuz Labs offers a helper CLI tool called labctl, allowing you to use your favorite text editor (or a full-featured IDE) to write content from the comfort of your local machine.

Install labctl CLI

curl -sf https://labs.iximiuz.com/cli/install.sh | sh

This will download and install the latest version of the labctl CLI. You only need to do this once per workstation.

Authorize labctl

labctl auth login

This will open a browser window asking you to authorize labctl to access your account. You need to do it after a fresh install of labctl and repeat it whenever the auth session expires.

Pull challenge content

labctl content pull challenge networking-find-listening-port-24f244e3

This will create a local copy of the challenge content in a directory named networking-find-listening-port-24f244e3. You only need to do this once per challenge.

Stream your changes

labctl content push -fw challenge networking-find-listening-port-24f244e3

Run this command in a separate terminal to continuously upload your changes to the server while editing the challenge in your favorite text editor or IDE.

You can also use labctl to create, list, and delete your content. Learn more about the available commands: labctl content --help

Start challenge