Connecting to minecraft server running on CentOS 8, please help (!)

[MrPotatoFace]

After some hassle, I managed to download CentOS on an old laptop of mine, as well as running a minecraft server after accepting the EULA. The problem is that I can't connect to it. I followed this guide for CentOS 8: https://linuxhint.com/install_centos_8_server/, this guide for sever: https://www.hostinger.com/tutorials/how-to-setup-minecraft-server#How-to-Make-a-Minecraft-Server-on-Linux, and finally portforwarded port 25565 to said laptop. Note that I am using the version of CentOS with no graphical interface and I did not get to install Screen. After reading this: 

I downloaded tmux instead (simply replacing the word screen with tmux), but did not end up using it, simply skipping it in tutorial about server. I seem to be having the same issue as this guy: https://forums.centos.org/viewtopic.php?t=59003, however, when trying their solution I simply get "Authorization Failed."

"Make sure polkit agent is running or run the application as superuser."

I am a big noob when it comes to Linux and all this other stuff, but I have run a minecraft server om my main PC for me and my friends before. I have been at this for hours and I really appreciate any help I can get!

[Eigenvektor]

10 minutes ago, MrPotatoFace said:

Note that I am using the version of CentOS with no graphical interface and I did not get to install Screen.

Screen is a command line tool and does not require a graphical interface. It allows you to run a command (e.g. in an SSH session) and detach from that session so that it continues running even though you're disconnected.

 

Have you checked whether the required ports are open in the firewall of the CentOS 8 machine? Try "sudo iptables -vL", this should tell you whether a firewall is active and which ports are allowed in.

 

Can you give a bit more details about which commands you've tried and what the exact result is?

[Master Disaster]

Did a bit of Googling and it seems like Screen is stored in the EPEL (Extra Programs for Enterprise Linux) Repo which isn't enabled by default.

 

Edit - This change was made for RHEL/CENTOS 8 and the guide you are following is for CENTOS 7 which is why the method it states doesn't work anymore.

 

You need to do

dnf install epel-release -Y

to enable it then you can pull Screen with

dnf install screen -Y

 

[MrPotatoFace]

2 minutes ago, Eigenvektor said:

Screen is a command line tool and does not require a graphical interface. It allows you to run a command (e.g. in an SSH session) and detach from that session so that it continues running even though you're disconnected.

 

Have you checked whether the required ports are open in the firewall of the CentOS 8 machine? Try "sudo iptables -vL", this should tell you whether a firewall is active and which ports are allowed in.

 

Can you give a bit more details about which commands you've tried and what the exact result is?

Checked ports? no clue. the command you suggested return 3 text chunks;

 

Chain INPUT (policy ACCEPT 20026 packets, 40M bytes)

 pkts vytes target    prot opt in    out     source

same thing repeats 2 times, except with:

... FORWARD ... 0 ... 0

&

... OUTPUT ... 5039 ... 395K

 

I've tried the solution person with firewall issues was suggested, that is when i get the error message.

[MrPotatoFace]

4 minutes ago, Master Disaster said:

Did a bit of Googling and it seems like Screen is stored in the EPEL (Extra Programs for Enterprise Linux) Repo which isn't enabled by default.

 

You need to do

dnf install epel-release -Y

to enable it then you can pull Screen with

dnf install screen -Y

 

Ok, now it says it needs to be run with superuser priviliges (under the root user on most systems) but I am logged into the only user(which is admin) and username of said user is displayed on last line in command prompt.

[Master Disaster]

sudo dnf install epel-release

then

sudo dnf install screen

 

You can miss the -Y, all this does is accept the pull without asking you.

[Eigenvektor]

1 minute ago, MrPotatoFace said:

Chain INPUT (policy ACCEPT 20026 packets, 40M bytes)

 pkts vytes target    prot opt in    out     source

This tells you, that the machine's default policy for incoming network connections is "ACCEPT". Essentially this means there is no firewall for incoming connections, it'll accept traffic on any network port. You didn't quote those parts for FORWARD and OUTPUT, but I'm going to assume they are ACCEPT also, which means the firewall is essentially inactive and not the source of your issues.

 

Install screen as @Master Disaster instructed, then try again running the Minecraft server. Once that is up an running you can use "netstat -tulpen" to see if it is listening on any port. If so, you should be able to connect to it.

[MrPotatoFace]

4 minutes ago, Master Disaster said:

sudo dnf install epel-release

then

sudo dnf install screen

 

You can miss the -Y, all this does is accept the pull without asking you.

That worked! screen now running (presumably as it should)

[MrPotatoFace]

7 minutes ago, Eigenvektor said:

This tells you, that the machine's default policy for incoming network connections is "ACCEPT". Essentially this means there is no firewall for incoming connections, it'll accept traffic on any network port. You didn't quote those parts for FORWARD and OUTPUT, but I'm going to assume they are ACCEPT also, which means the firewall is essentially inactive and not the source of your issues.

 

Install screen as @Master Disaster instructed, then try again running the Minecraft server. Once that is up an running you can use "netstat -tulpen" to see if it is listening on any port. If so, you should be able to connect to it.

Ok, screen is running, I used "netstat -tulpen" and the resulting list contains one line with 25565(minecraft port) in it:

Proto   Rev-Q   Send-Q   Local address   Foreign address   STATE       User     Inode      PID/Program name

tcp6     0            0              :::25565            :::*                        LISTEN     1000     82171     33583/java

Still can't connect to it, though

[Master Disaster]

Just now, MrPotatoFace said:

Ok, screen is running, I used "netstat -tulpen" and the resulting list contains one line with 25565(minecraft port) in it:

Proto   Rev-Q   Send-Q   Local address   Foreign address   STATE       User     Inode      PID/Program name

tcp6     0            0              :::25565            :::*                        LISTEN     1000     82171     33583/java

Still can't connect to it, though

Are you connecting internally or externally? Have you forwarded the port through your router firewall?

[Eigenvektor]

1 minute ago, MrPotatoFace said:

Ok, screen is running, I used "netstat -tulpen" and the resulting list contains one line with 25565(minecraft port) in it:

Proto   Rev-Q   Send-Q   Local address   Foreign address   STATE       User     Inode      PID/Program name

tcp6     0            0              :::25565            :::*                        LISTEN     1000     82171     33583/java

Still can't connect to it, though

Minecraft is a Java application, so that is probably it. It is listening on port 25565.

 

Is there an equivalent entry for tcp4? Because right now it seems to be only listening on IPv6. Are you using IPv6 on your internal network?

[MrPotatoFace]

1 minute ago, Master Disaster said:

Are you connecting internally or externally? Have you forwarded the port through your router firewall?

Yes, I have forwarded the port(TCP + UDP), and I am trying to connect on my other PC using the local iPv4 address of the laptop running the server.

[MrPotatoFace]

Just now, Eigenvektor said:

Minecraft is a Java application, so that is probably it. It is listening on port 25565.

 

Is there an equivalent entry for tcp4? Because right now it seems to be only listening on IPv6. Are you using IPv6 on your internal network?

There are no entries for tcp4 in the list, as far as I know I'm only using IPv4 on my network, that is at least what I have been using when trying to connect to the server.

[Eigenvektor]

Just now, MrPotatoFace said:

There are no entries for tcp4 in the list, as far as I know I'm only using IPv4 on my network, that is at least what I have been using when trying to connect to the server.

Right now Minecraft seems to only be listening on the machine's IPv6 interface, which is why you can't connect to it through IPv4.

 

You could try this one: https://superuser.com/questions/453298/how-to-force-java-to-use-ipv4-instead-ipv6

[MrPotatoFace]

49 minutes ago, Eigenvektor said:

Right now Minecraft seems to only be listening on the machine's IPv6 interface, which is why you can't connect to it through IPv4.

 

You could try this one: https://superuser.com/questions/453298/how-to-force-java-to-use-ipv4-instead-ipv6

Ok, to be honest I can't make that much sense of that thread. I know it may be a lot to ask, but I really want to get this going even though I get the felling I don't have the background knowledge necessary. I would really appreciate it if you could explain what commands I should use.

[Eigenvektor]

14 minutes ago, MrPotatoFace said:

Ok, to be honest I can't make that much sense of that thread. I know it may be a lot to ask, but I really want to get this going even though I get the felling a don't have the background knowledge necessary. I would really appreciate it if you could explain what commands I should use.

You should only need put the line below into the file ".bash_profile" in the home directory of the user that you use to run the Minecraft server. When you have added the line, you can reload the file by doing "source ~/.bash_profile". Replace "~" with the user's home directory, if you're using a different user than the one you're signed in with.

 

export _JAVA_OPTIONS="-Djava.net.preferIPv4Stack=true"

Afterwards you need to restart the Minecraft service and it should now default to using IPv4 instead of IPv6.

[MrPotatoFace]

7 minutes ago, Eigenvektor said:

You should only need put the line below into the file ".bash_profile" in the home directory of the user that you use to run the Minecraft server. When you have added the line, you can reload the file by doing "source ~/.bash_profile". Replace "~" with the user's home directory, if you're using a different user than the one you're signed in with.

 

export _JAVA_OPTIONS="-Djava.net.preferIPv4Stack=true"

Afterwards you need to restart the Minecraft service and it should now default to using IPv4 instead of IPv6.

Ok, I am about 95% sure I did this correctly, but I still cannot connect, and "netstat -tulpen" still doesn't show any tcp4.

[MrPotatoFace]

Ok, new day and for some reason things have changed. After restarting the laptop(now server I guess) I opened screen and attempted to run the server using the following command:

 

java Xmx4G Xms4G -jar server.jar nogui

 

This resulted in the following output:

Picked up _JAVA_OPTIONS: -Djava.net.preferIPv4Stack=true

Error: Could not find or load main class Xmx4G

Edit: Oops, typo(- before Xmx and Xms). Server now running, but I still can't connect to it.

[Eigenvektor]

Can you try again what the output of the following two commands is:

ip addr show

netstat -tulpen

The first one should show you the IP address(es) of the server, the second one once again the listening port.

 

With the IP address and port you could try simply connecting to it with telnet from another machine. So "telnet <ip> <port>", see if you can connect or what kind of error you get.

[LogicalDrm]

-> Moved to Linux, macOS and Everything Not-Windows

[MrPotatoFace]

Ok, I formatted and removed every partition from the drive, reinstalled CentOS, redownloaded the server but did everything according to this guide instead: https://www.spinup.com/setting-up-a-minecraft-server-on-centos-8/. Everything now works great! Thanks a lot to @Eigenvektor & @Master Disaster for all the help. Edit: I realized afterwards that may have sounded sarcastic, that was truly not the intention. I have however run into a small issue: I cannot for the life of me prevent the machine from sleeping when I close the lid. I have changed pretty much every setting related to the lid in "/etc/systemd/logind.conf" to "ignore". I have also run this command: "systemctl restart systemd-logind", which asks for authorization and then turns my blinking underscore-cursor red. It does not help however. Edit: solution turned out to be uncommenting the lines in the .conf file by removing the #.

[Eigenvektor]

16 minutes ago, MrPotatoFace said:

Edit: I realized afterwards that may have sounded sarcastic, that was truly not the intention.

No worries Sometimes starting from scratch is the easiest option.

 

Not really familiar with power settings, since I'm primarily a desktop user. Could you check in the laptop's BIOS if there's some setting that might still cause it to go to sleep?

 

The settings in logind.conf should be the correct ones, as far as I could find. You probably found this link already: https://unix.stackexchange.com/a/52645, this is pretty much what you tried already. You could maybe try checking the kernel.log (see question on stackexchange) to see if there are entries related to sleep mode still.

[MrPotatoFace]

37 minutes ago, Eigenvektor said:

No worries Sometimes starting from scratch is the easiest option.

 

Not really familiar with power settings, since I'm primarily a desktop user. Could you check in the laptop's BIOS if there's some setting that might still cause it to go to sleep?

 

The settings in logind.conf should be the correct ones, as far as I could find. You probably found this link already: https://unix.stackexchange.com/a/52645, this is pretty much what you tried already. You could maybe try checking the kernel.log (see question on stackexchange) to see if there are entries related to sleep mode still.

I checked the BIOS, but they seem very limited. Couldn't find the correct settings. Could it be that the BIOS have been intentionally limited, since this is a laptop? I couldn't find any "expert" or "advanced" mode either.

[MrPotatoFace]

15 hours ago, MrPotatoFace said:

I checked the BIOS, but they seem very limited. Couldn't find the correct settings. Could it be that the BIOS have been intentionally limited, since this is a laptop? I couldn't find any "expert" or "advanced" mode either.

Figured it out! Turns out all the lines in the logind.conf file are commented out, something I probably should have recognized, but I'm really only used to the // for comments. Anyways, changing this fixed it and the server now runs like a charm!