Failed to connect to the server. Reason: This is often caused by UDP port 20595 not being forwarded on the host side, by a firewall, or antivirus software.

[gui456wSERTDYF]

I am not a developer, I am a user, so sorry if this does not go here.

I really enjoy the game and usually I experience no problems. However, sometimes I cannot connect to multiplayer games and I keep receiving the message that is shown in this screenshot:

This happens completely randomly (to me), and it lasts during a whole day usually. When it happens I cannot also host a game, the other players receive this message. But they can connect to other games or host their own games. If this happens on one day, the next day usually there is no problem at all, I can connect to any game and can host games with no problem. I have googled this problem with not much success.

I have tried all the possible combinations with a friend:

1. Me hosting with "Use STUN...".
2. Me hosting without "Use STUN...".
3. My friend hosting with "Use STUN...".
4. My friend hosting without "Use STUN...".

and none of them worked.

I am using this version of 0AD:

in Ubuntu 20.04.

 

EDIT: My solution (NOT WORKING ANYMORE)

I have found that if I restart my phone then this problem is solved. I usually connect using my mobile hotspot.

 

Edited August 4, 2022 by gui456wSERTDYF
Found a solution to my problem

[JmNzhl]

I also encountered this problem. Is your problem solved?

[gui456wSERTDYF]

I usually connect through my phone using the hotspot Wi-Fi. I discovered that if this problem happens, restarting the phone is a solution. Restarting the computer does not solve the problem for me.

I guess that, in analogy with my solution, restarting your modem or whatever device you use to connect can provide a solution.

[gui456wSERTDYF]

On 11/11/2020 at 7:59 AM, gui456wSERTDYF said:

I usually connect through my phone using the hotspot Wi-Fi. I discovered that if this problem happens, restarting the phone is a solution. Restarting the computer does not solve the problem for me.

I guess that, in analogy with my solution, restarting your modem or whatever device you use to connect can provide a solution.

Just want to let the world know that this is not working anymore since 0AD 24. I don't know if something changed or is it just random.

[leopard]

@stan I am facing this issue now, is there anything I can do. I was able to connect with a VPN but now trial period is over and I am not planning to buy VPN, I tried to contact the ISP no response so far.

[Stan`]

@Dunedan any clue?

[gui456wSERTDYF]

I am still facing this problem and it is frustrating. It seems to be completely random, some days I can play (join or host) any game I want, several games per day. Other days I cannot join any game at all and people cannot join my games, but they can play among themselves (not always anyway). Other days some games I can join, some others I can't. Today I played a game some hours ago, no problems; now I wanted to play again and just keep getting this. So I didn't play.

What can I try to debug this problem? Things already done (because sometimes they work):

• Restart 0AD.
• Restart computer.
• Connect via a VPN.

I don't have a router. I always connect via the hotspot of my phone with 4G.

[gui456wSERTDYF]

Why can this problem be random? I.e. some days it works, others not, even with the same host. I am not aware of changing anything in my side, nor in the host side.

[Norse_Harold]

Good question. You care enough about this problem to post follow-up comments about it. That's good.

Now the true test. Do you care enough about it to learn about networking fundamentals and conduct detailed troubleshooting?

I suggest learning things like what are UDP protocol, UDP source and destination ports, IP addresses, firewalls, routing, transparent proxy (Network Address Translation), etc.

You could install Wireshark and capture traffic while doing controlled experimentation.

Edited August 13, 2022 by Norse_Harold

[gui456wSERTDYF]

Yeah, I can. It will take some time though. Do you have suggested bibliography? I will start in Wikipedia.

Another issue I experience quite frequently which is probably related is that I host a game, people can connect without issues (up to 8 players) and it works absolutely fine for about 30-60 minutes. Then, suddenly, one by one players loose connection and cannot come back. This process takes between 5 and 15 minutes per player, and does not affect all players but some.

BTW, yesterday I knew about other player that was experiencing the port connection issues with all games except mine, don't ask me why. Of course he did not come to the forum to report this.

[gui456wSERTDYF]

In case someone else ends up reading here, my issue was solved when I changed my internet provider. I did not change it due to 0AD but it turned out that now I don't experience this issue anymore.

[seeh]

in newer fritz-box seems not possible to set it up with IPv4 but with IPv6. i hope it will working with IP6.

internet > filter >freePorts > add device for freePort >

1. choose your pc
2. press 'new port'
   1. app: other
   2. your title. doesn't matter
   3. Protocol: UDP
   4. check for IPv6 only
   5. set 20595 to 20595
   6. press ok
3. press ok

i hope it works for you

[Norse_Harold]

There is an FAQ answer to this question here. Scroll down to read the answer to "Failed to connect to the server. UDP port 20595 not being forwarded." Anyone who still needs help, talk to me on IRC when I'm responsive.

[seeh]

On 07/06/2023 at 6:58 PM, Norse_Harold said:

FAQ answer to this question here. Scroll down to read the answer to "Failed to connect to the server. UDP port 20595 not being forwarded."

thanks

Edited June 12, 2023 by seeh
works now at my home also for IPv4