Kirrus

Try opening a terminal, dragging and dropping the .sh script into it, and then hitting enter. Let us know what the error message reports.

Try opening a terminal, dragging and dropping the .sh script into it, and then hitting enter. Let us know what the error message reports.

Thanks! Ok, you can drop the port and the TXT record now. I've added your IP to the whitelist. You should be able to get your server listed now. You'll need to restart the server, so it can resend the initial server-submission, if it fails once, it's designed to not try again till it's restarted.
 
Please note, standard warning (that I don't expect to need to act on), if we detect errant traffic coming from your IP, we'll block first and ask questions never. Other than that, game on!

I'll reply inline below:

This shouldn't be happening. Make sure you *don't* set a server name or description, that should help.  

leave the server 'open' with no registration. All people have to do then is enter your IP (or domain name, if your server has a domain or subdomain pointed at it) in the IP/Host field, their username, and then connect. They don't need to specify a password.
 

Awesome!

If you post your solution in a new post, you can then hit 'mark solved' against it. It automatically updates the title, and puts the answer in a big green box at the top of the post.

I have been searching and found out that a timeout is mostly caused by a connection that is either denied or unsuccesfully established. Refering to that, and with past experience with firewall issues, I digged deeper into my firewall.
 
For people with AVG-antivirus, THIS is the solution:
Just disabling firewall in the mini-tray icon list is not enough. It's AVG, this program will NEVER shut off at full ratio. With this in mind (as I knew this from previous experience) I knew it had eventually something to do with SOMETHING blocking the download. When you get the "timeout downloading zip" error, it's got to do something at your end blocking the connection.
 
To solve the issue:
1. Go to AVG-user panel (via mini-tray icon, lower-right corner). From there go to the tab "extra" and click Advanced settings.
2. Left in the menu, scroll down to the bottom. There you will find something called "Disable security for AVG temporarily", click on it.
3. Check the box that's saying: "Temporarily disable AVG security", and set the timer to max (15 minutes).
4. Open Project Zomboid and connect to a server. Now that AVG is FULLY disabled, the connection will not be blocked by it, and you will be able to connect with the server!
5. ENJOY!
 
6. The only downside however, is that you need to do disable it EVERY time you want to join a server.
 
(If you find it hard to understand my instructions, please follow this tutorial: www.avg.com/ww-en/faq.num-3857)
 
If you have another Anti-Virus program, consider to Google HOW TO DISABLE IT FULLY. I am 99% SURE it will fix the issue!

If you're an admin, you get to speed through the map. Generally speaking, you should only login an admin-level account when you need it, not play on it all the time

As root, edit the following file:
/etc/security/limits.conf
 
Add these lines if they're not already there;
*               soft     nofile            8192
*               hard     nofile           32768
 
Log off the user you're using to run the server, and log it back on, or reboot your server

We've had a brief initial talk to a server hoster based in the states. It's likely that it'll come along, need to add some extra features for hosts.

That's probably it running out of memory. If you can, bump these up -Xms2048m -Xmx2048m
Making it a bit more graceful when it runs out is on the todo list.

The first port is UDP. All ports after that are TCP.