Ports for VPS are no longer open

I have an ubuntu instance on the oracle cloud infrastructure on which I've been running a minecraft server. It's been working for a couple months now and I had no problem opening ports on their website & on the system when setting it up.

All of the sudden though, the 25565 port appears to be closed. I haven't touched it since the last time it was working. All the ports on the website are still open and they should still be on the system.

Only thing I found odd is when I try to add the ports again for example with this command:

sudo firewall-cmd --permanent --zone=public --add-port=25565/udp

It outputs an error: Error: DBUS_ERROR: Failed to connect to socket /run/dbus/system_bus_socket: No such file or directory

I have no idea what could have caused this. Any ideas on how to reopen the port? Sorry I'm not very knowledgeable when it comes to this. I couldn't get support from oracle since they don't offer support to free accounts, so I'm asking here.

My ubuntu version is Ubuntu 22.04.1 LTS

I had the same problem and was able to fix it.

First, check D-Bus status:

systemctl status dbus

If it's not running, which is likely, then run it:

sudo systemctl start dbus

Then check Firewalld status:

sudo firewall-cmd --state

If it's not running, which again is likely, then run it or just restart your instance.

I was able to test that I can open UDP port 25565 and pass traffic from my home network to one of my Oracle Cloud free tier compute instances. My configuration might be a bit different than yours since I am running Ubuntu 20.04.6 LTS and the instance/virtual machine was created in March of 2021. I mention the creation time since it appears that since their policy on blocking outbound port 25 (SMTP) has changed for instances created after mid June 2021 (https://docs.oracle.com/en-us/iaas/releasenotes/changes/f7e95770-9844-43db-916c-6ccbaf2cfe24/ and https://support.oracle.com/knowledge/Oracle%20Cloud/2787393_1.html), I wonder if they may have also started blocking other ports on new instances. Regardless, here are the steps I took that seemed to work:

1. Add an ingress rule: From the Oracle Cloud portal menu in the upper left, click compute, then instances. Click on your instance name. Then on that first tab, under Instance Information, under the sub-heading Instance Details, look for the text Virtual Cloud Network and click on the link to the right of that text. You should now be in the correct virtual cloud network but if not, you can see all virtual cloud networks from the main menu > Networking > Virtual Cloud networks.

2. Once in the correct virtual cloud network page, on the lower left column under Resources, click on Security Lists. Click on the Default Security List for link.

3. click on the Add Ingress Rule button. I left all defaults except for the following changes: Source CIDR: 0.0.0.0/0 IP Protocol: UDP Destination Port Range: 25565 Description (optional): test port 25565 ingress rule

4. From the virtual machine instance console (over Cloud Shell / SSH / etc) type the following command to allow port 25565 through the VM's firewall:

   sudo iptables -I INPUT 6 -m state --state NEW -p udp --dport 25565 -j ACCEPT

5. At this point the port should be open. But to test traffic through it I downloaded iPerf2 from https://iperf.fr/iperf-download.php to my local machine. (I used version 2.0.9 32-bit but any version, even iPerf3 should work). I also installed iPerf2 on the VM via APT:

   sudo apt-get install iperf

6. I then typed the following command on the VM to start an instance of iPerf2 in server mode listening on UDP port 25565:

   iperf --udp -s -p 25565

7. Then on my PC, after unzipping iPerf2 v 2.0.9 32-bit, opened a command prompt, navigated the proper folder and then typed the following command to have iPerf2 start in client mode and connect to the Oracle Cloud compute VM's public IP address on UDP port 25565:

   iperf --udp --client -p 25565

Here are the results I received:

Log from the client (local PC using home internet connection):

---------------------------------------------
Client connecting to <Oracle Cloud VM Public IP>, UDP port 25565
Sending 1470 byte datagrams, IPG target: 11215.21 us (kalman adjust)
UDP buffer size: 63.0 KByte (default)
---------------------------------------------
[  3] local 192.168.200.15 port 49922 connected with <Oracle Cloud VM Public IP> port 25565
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  1.25 MBytes  1.05 Mbits/sec
[  3] Sent 893 datagrams

Log from the server (Oracle Cloud Compute Instance Ubuntu 20.04 VM):

user@host:~$ iperf --udp -s -p 25565                         ---------------------------------------------
Server listening on UDP port 25565
Receiving 1470 byte datagrams
UDP buffer size:  208 KByte (default)
---------------------------------------------
[  3] local 10.0.0.2 port 25565 connected with <My Home ISP Public IP> port 49922
[ ID] Interval       Transfer     Bandwidth        Jitter   Lost/Total Datagrams
[  3]  0.0-10.0 sec  1.25 MBytes  1.05 Mbits/sec   1.978 ms    0/  893 (0%)

I hope this helps you or others with similar issues!