Transfer Module

Overview

The transfer module allows you to transfer players from one server to another, without the need of additional proxy setups, using the transfer packet. We've also introduced a ping packet to get a players ping to other servers.

• Adds the ability to use the Transfer Packet and Ping Packet on players.
  • Ability to transfer players from one server to another
  • Ability to ping other servers, to get a players ping time to those servers.

When you combine the usage of the ping packet and transfer packet, you can do connection-based optimizing for your players.

Transfer Consent DNS Record

Instead of requiring users to click "Accept" on the transfer popup, transfers can also be auto-accepted by the target server. This produces a smoother user experience, without the friction of manually needing to accept.

The intent of the confirmation screen is to ensure users are aware they're changing to a third-party server. However, many use cases of the transfer packet involve moving around the same server, or between IPs owned by the same party. In these cases, the confirmation can be skipped entirely if the target server has whitelisted the sender server in a mc_transfer_accept_from TXT DNS record.

Building the whitelist

When attempting to transfer to a server, Lunar Client first performs a DNS lookup for TXT records at the target server's IP. For example, if directed to connect to na.lunar.gg, the client will send a TXT DNS query for na.lunar.gg.

The results of this query are split by a comma (,), and added to the whitelist. The same query is then sent for any parent domains. For example, if the user is connecting to foo.na.lunar.gg, the effective whitelist of sender servers is the combination of the results for foo.na.lunar.gg, na.lunar.gg, and lunar.gg.

This hierarchy method is intended to allow transfering to dynamically generated subdomains, without requiring a TXT record be set on each of them.

For example, if the following DNS records are present in your DNS provider:

• na.lunar.gg TXT mc_transfer_accept_from=*.hypixel.net
• lunar.gg TXT mc_transfer_accept_from=*.lunar.gg,lunar.gg

When transfering to na.lunar.gg, the effective whitelist would be:

• *.hypixel.net
• *.lunar.gg
• lunar.gg

When transfering to lunar.gg (or any other subdomains, like eu.lunar.gg), the effective whitelist would be:

• *.lunar.gg
• lunar.gg

Checking the whitelist

Once a whitelist of allowed sender IPs has been built, Lunar Client checks if the IP the user is currently connected to is in this whitelist. If it is, the transfer is accepted immediately. If it is not, the user receives a transfer popup.

Note that wildcards are accepted. For example, *.lunar.gg will allow na.lunar.gg, eu.lunar.gg, sa.lunar.gg, etc. to transfer to this server.

Practical Examples

If you own example.com and want to auto-accept transfers between any subdomains, create the following records:

• example.com -> TXT mc_transfer_accept_from=*.example.com,example.com

If you own example.com and server.net, and want to auto-accept transfers between them, create the following records:

• example.com -> TXT mc_transfer_accept_from=*.example.com,example.com,*.server.net,server.net
• server.net -> TXT mc_transfer_accept_from=*.example.com,example.com,*.server.net,server.net

Integration

Using the Transfer Packet

public void transferExample(Player viewer) {
    Optional<ApolloPlayer> apolloPlayerOpt = Apollo.getPlayerManager().getPlayer(viewer.getUniqueId());
 
    if (!apolloPlayerOpt.isPresent()) {
        viewer.sendMessage("Join with Lunar Client to test this feature!");
        return;
    }
 
    // Sending the transfer request to the player, to transfer them to "mc.hypixel.net"
    this.transferModule.transfer(apolloPlayerOpt.get(), "mc.hypixel.net")
        .onSuccess(response -> {
            String message = "";
 
            switch (response.getStatus()) {
                case ACCEPTED: {
                    message = "Transfer accepted! Goodbye!";
                    break;
                }
 
                case REJECTED: {
                    message = "Transfer rejected by client!";
                    break;
                }
            }
 
            viewer.sendMessage(message);
        })
        .onFailure(exception -> {
            viewer.sendMessage("Internal error! Check console!");
            exception.printStackTrace();
        });
}

Using the Ping Packet

public void pingExample(Player viewer) {
    Optional<ApolloPlayer> apolloPlayerOpt = Apollo.getPlayerManager().getPlayer(viewer.getUniqueId());
 
    if (!apolloPlayerOpt.isPresent()) {
        viewer.sendMessage("Join with Lunar Client to test this feature!");
        return;
    }
 
    // Sending the ping request to the player, for the servers "mc.hypixel.net" & "minehut.com".
    this.transferModule.ping(apolloPlayerOpt.get(), Lists.newArrayList("mc.hypixel.net", "minehut.com"))
        .onSuccess(response -> {
            for (PingResponse.PingData pingData : response.getData()) {
                String message = "";
 
                switch (pingData.getStatus()) {
                    // Displays successful ping request to display the server IP and the players ping to that server.
                    case SUCCESS: {
                        message = String.format("Ping to %s is %d ms.", pingData.getServerIp(), pingData.getPingMillis());
                        break;
                    }
 
                    // If the ping request times-out
                    case TIMED_OUT: {
                        message = String.format("Failed to ping %s", pingData.getServerIp());
                        break;
                    }
                }
 
                viewer.sendMessage(message);
            }
        })
        .onFailure(exception -> {
            viewer.sendMessage("Internal error! Check console!");
            exception.printStackTrace();
        });
}