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network-programminggoogle-cloud-platformvirtual-machinegcloudubuntu-18.04

Google cloud VM ports won't open

I tried to open all ports for incoming trafic in my Google Cloud VM.

I've added a firewall rule to default network in GCP.

Firewall rule config: enter image description here

Then I've created a VM using the default network.

Unfortunately, after I ssh into my VM and scan for open ports, nmap says that only one is open.

piotr@worker:~$ nmap localhost

Starting Nmap 7.60 ( https://nmap.org ) at 2021-12-06 17:17 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00011s latency).
Not shown: 999 closed ports
PORT   STATE SERVICE
22/tcp open  ssh

Nmap done: 1 IP address (1 host up) scanned in 0.06 seconds

Also when I try to telnet from my local machine, I fail on all ports, succed only on port 22.

Should I open ports manually with tool like ufw (VM is a Ubuntu 18.0.4).

Or am I doing something else wrong?

Solution

  • I think you are confusing the action of opening a firewall port to allow traffic and opening a port by listening for connections. Your VM needs a service (software) listening on a port to act upon something connecting to that port. For example a web server for port 80 or 443.