Getting a raw server IP address

[yuto0214w]

Is there any way I can get multiplayer server IP address, in a form of, like "1.2.3.4"?

I'd like to validate it and make it only work in certain server.

[sFXprt]

  On 5/12/2023 at 1:53 AM, yuto0214w said:

Is there any way I can get multiplayer server IP address, in a form of, like "1.2.3.4"?

I'd like to validate it and make it only work in certain server.

Expand  

MinecraftServer#getLocalIP()?

[warjort]

I believe getLocalIp() is just what is configured in the server.properties. It's likely the empty string unless the user has changed it?

 

If you really want to know what addresses (it can be more than one) the server it is actually bound to,

then you will have to do write some code to see what netty transport layer minecraft is using and then look at the Netty classes for each transport to get the information.

But it might not be using a standard transport, e.g. a mod might have changed it: https://www.curseforge.com/minecraft/mc-mods/essential-mod

 

Using an ip address is very brittle for your usecase anyway. Anybody can configure their server to have whatever ip address they want, then use NAT to translate to their real ip for external use.

A MAC address would be better, but that can be spoofed too with more effort.

    public static void main(String[] args) throws Exception {
        // Standard java way to get the host ip
        System.out.println(InetAddress.getLocalHost().getHostAddress());
        // Netty class to print the MAC address
        System.out.println(MacAddressUtil.formatAddress(MacAddressUtil.bestAvailableMac()));
    }

None of this really has anything to do with Minecraft/Forge. You would be better off asking in the Netty forums or a general java or networking one.

[warjort]

One other point:

If you are planning to use this information to check against some kind of central database owned by you, you will need to get the user's permission to collect this information (even if it is anonymous).

And you will need to treat any stored information with the same security that you would when storing a user's password.

[yuto0214w]

Let me note that this mod is client-side. Sorry that I caused a misunderstanding.

Let's say player connect to "abcd.net" which leads to "1.2.3.4:25565".

I want to get "1.2.3.4:25565" string or whatever and check it if it's certain server.

[warjort]

I am not sure how to do that,

but it will be something like (untested code):

        var packetListener = Minecraft.getInstance().getConnection();
        if (packetListener != null && packetListener.getConnection().getRemoteAddress() instanceof InetSocketAddress inetSocketAddress) {
            System.out.println(inetSocketAddress);
        }

Or there is also

        var packetListener = Minecraft.getInstance().getConnection();
        if (packetListener != null) {
            System.out.println(packetListener.getServerData().ip);
        }

But the latter is probably the "abcd.net"?

 

If those don't give you what you want, you can use packetListener.getConnection().channel() to get the Netty implementation.

Edited May 12, 2023 by warjort

[yuto0214w]

First code gave me the string I needed. Thank you a lot!

[jaxox]

well I tried the first code (but in java 8 )

but it didnt work for my case

 

@SubscribeEvent
    public static void validServerIpCheck(FMLServerAboutToStartEvent event) {

        ClientPlayNetHandler packetListener = Minecraft.getInstance().getConnection();
        if (packetListener != null && packetListener.getConnection().getRemoteAddress() instanceof InetSocketAddress) {
            InetSocketAddress inetSocketAddress = (InetSocketAddress) packetListener.getConnection().getRemoteAddress();
            if (!inetSocketAddress.getAddress().getHostAddress().equals("1.2.3.4")) {
                event.getServer().close();
            }
        }
    }

anyone know the solution?