So yesterday I proposed to a group of friends to play Heroes 4. We all had the same folder of the game. Everything was going great until the moment of the online connection.

We did it via TCP / IP. First we tried with direct connection, that is, the host gave me permission to enter to his network to play, and I could not see the room created. Then we tried Hamachi, and we couldn't.

I have looked for solutions on forums, websites and Discord servers and we have tried the following:
-To set the Hamachi network to the highest priority, so we grab the network with the highest priority, and stick to it.
-We tried to play the game without extra files (visual mods like the resolution one for 16:9 monitors, extra maps, etc).
-Different ports (the default one, 4437 if I'm not wrong and 2303).
-Different IP's: the public and private one.
-We both tried to be the Host of the game.
-We checked DirectPlay (maybe it was disbled, but is wasn't)

I don't really know what to do more. I just want to play online via Hamachi and it is impossible. And the funny thing is that we played other games using Hamachi and we had zero problems. And obviously, we give permission to the firewall.

If anyone who plays Heroes 4 online can give me some information that I'm missing I would be very happy to read it, but I find very strange to play a simple videogame online.

Okay, when someone in my group has time to test it, I'll tell you if that's the problem.

Thank you for your fast reply!

I'm looking to what you said and, when the game runs it automatically appears the firewall window to give permissions to the program. So when we both give those permissions we already give an exception...
https://gyazo.com/c9405241f18f2031e1c2eb6aa166271d?token=d60069d3bbe2437fb02a749f61ce8b0c

Also, giving an exception to the antivirus makes nonsense. My antivirus never told me anything about Heroes 4, there is zero conflicts with it... it is not like other kind of programs that are cracked and they need to be excluded...

The problem was the Public/private firewall of Windows. The thing is that idk how to play without desactivating 100% my firewall

In the Windows Control Panel (not Settings), go to Windows Defender Firewall. In the left sidebar, choose "Allow an app or feature through Windows Defender Firewall". Then, choose the "Change Settings" option, for which you need an administrator-level account in Windows.

Below the list of current apps the Firewall recognizes, choose "Allow Another App", browse to your Heroes IV directory and select Heroes4.exe.

Make sure you allow it in private and public networks by ticking the right boxes and that's that. You won't need to deactivate the entire firewall. This goes for any other application you have this issue with.

@Dahicarr - basing on my experience (issues with playing games online), usually it's not about firewall/antivirus, but "unlocking" ports.

And to be more specific - about thing called "redirecting ports" (przekierowanie portów). It's usually set in the router settings... That is if your internet provider gives such possibility

Check with your internet provider website (or other way, e.g manual you had included to router), how can you access router settings (usually it's address like 192.168.1.1, you're entering it in the web browser, just like that, only numbers and dots). I see that you've mentioned in the first post about ports needed specifically for Heroes of Might and Magic IV, so you already know which ports you need to "redirect".

It's a guess, but to be honest, usually after fighting with internet provider to have access to redirecting ports (by some reason my provider hid this option in settings, I had to call 3 times to make them unlock it for me), this option turned out to be the major reason why I couldn't successfully play online in older games.

This video on YouTube helped me and my friend "Hamachi Relayed Tunnel Fix 2021 - Hamachi Minecraft Server"