People cannot join my hosted games

[cl2488]

When I host a game in the lobby, other players cannot join my game. But I can join the games hosted by other players. I use MacOS Big Sur version 11.2.3. Do you have an idea what the problem is and how I can fix it?

[Langbart]

#5306 UDP Problem 

@elexis wrote this:

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If you forward the port, everyone will be able to join you. If you use STUN when hosting, probably many but not everyone will be able to join you. If you can't join someone else's game, there's nothing you can do about it other than informing the host that he should forward or host your own game.

Port forwarding looks like this on my router, it might look different on yours. 

[cl2488]

What is port forwarding? Can you explain more about it? How to do port forwarding in a Mac?

I use STUN, but people still cannot join my game. 

[cl2488]

Never mind. I have fixed the problem by using port forwarding. Thanks for your reply, which is helpful.

[Langbart]

8 hours ago, cl2488 said:

What is port forwarding? Can you explain more about it? How to do port forwarding in a Mac?

I regularly get requests from users on #0ad asking for help with this problem, below is a small collection of other websites. I will probably send them the link to this thread so they can more easily find out what port forwarding is and how to do it. Thanks for asking.

portforward.com - How To Forward a Port

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A port forward is a way of making a computer on your home or business network accessible to computers on the internet, even though they are behind a router. It is commonly used in gaming, security camera setup, voice over ip, and downloading files. After you have forwarded a port you are said to have an open port.

 computer.howstuffworks.com -  How BitTorrent Works

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A firewall protects your system from intruders by disallowing unauthorized access to your computer's ports. A port is a way for Internet communications to travel into and out of your computer. Ports are numbered, and each communication type has a standard port number. BitTorrent also uses specific port numbers, normally ports 6881 through 6889. Because firewalls block these ports by default, you'll need to configure your firewall to accept this incoming traffic in order to receive .torrent files. You may also have to enable port forwarding of your computer's IP address for ports 6881 through 6889 so that other BitTorrent computers can find you.

r/explainlikeimfive (18/Aug/2018) - ELI5: What are ports? Port forwarding? What are they and what are they used for?

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Any internet device has an IP address (something like 198.51.63.25). Think of it like a house. And you can go out and visit other houses or you could even get visitors to your house.

Now to enter a house you, of course, the house needs doors. And your "internet house" has 65535 of them. Most of them remain closed the whole time (web servers mostly have ports 80 (http) and 443 (https) open). All open ports lead to a room. Two may even lead to the same room. It's all a matter of configuration.

So in order to let someone in your house, you need to open a door so they can come in.

Many ports have standardised purposes like for example:

• 21 - FTP (File Transfer Protocol)
• 22 - SSH (A protocol to connect to other computers/servers to control the system or some parts of a system)
• 80 - HTTP (All websites which don't have a green lock in the address bar)
• 443 - HTTPS (All websites which have a green lock in the address bar)

stackoverflow.com (5/9/2012) - When is port forwarding necessary?

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Port forwarding is needed when a machine on the Internet needs to initiate a connection to a machine that's behind a firewall or NAT router. If the connection is initiated by the machine behind the firewall, the firewall/router automatically recognizes the reply traffic and sends it to the machine that opened the connection.

But if a packet arrives on the external interface, and it's not a part of such a connection, the router needs to know what to do with it. By default, it will reject it. But if forwarding is configured for the port, that tells it what internal machine to send it to.

Put another way: you need port forwarding if you want to run a server behind the NAT firewall/router, you don't need it if you're just running a client.