Serverbound Packets

Overview

Players using Lunar Client may send packets to the server for specific Apollo modules, such as the PacketEnrichment Module and/or when the player is joining the server. This example demonstrates how to handle packets sent from the client that are related to Apollo while using JSON messages.

Additionally, the Transfer Module expects a response packet from the client after the server sends a request. For an example of how to handle roundtrip packets, visit Packet Roundtrip Example

Note that this method uses a different plugin channel for sending and receiving packets, which is apollo:json.

Integration

public class ApolloPacketReceiveJsonListener implements PluginMessageListener {
 
    private static final String TYPE_PREFIX = "type.googleapis.com/";
    private static final JsonParser JSON_PARSER = new JsonParser();
 
    public ApolloPacketReceiveJsonListener(ApolloExamplePlugin plugin) {
        Bukkit.getServer().getMessenger().registerIncomingPluginChannel(plugin, "apollo:json", this);
    }
 
    @Override
    public void onPluginMessageReceived(@NonNull String channel, @NonNull Player player, byte[] bytes) {
        JsonObject payload;
        try {
            payload = JSON_PARSER.parse(new String(bytes, StandardCharsets.UTF_8)).getAsJsonObject();
        } catch (Exception e) {
            return;
        }
 
        if (!payload.has("@type")) {
            return;
        }
 
        String type = payload.get("@type").getAsString();
        if (type.startsWith(TYPE_PREFIX)) {
            type = type.substring(TYPE_PREFIX.length());
        }
 
        if ("lunarclient.apollo.player.v1.PlayerHandshakeMessage".equals(type)) {
            this.onPlayerHandshake(payload);
        }
 
        // Packet Enrichment Module
        if ("lunarclient.apollo.packetenrichment.v1.PlayerAttackMessage".equals(type)) {
            this.onPlayerAttack(payload);
        } else if ("lunarclient.apollo.packetenrichment.v1.PlayerChatOpenMessage".equals(type)) {
            this.onPlayerChatOpen(payload);
        } else if ("lunarclient.apollo.packetenrichment.v1.PlayerChatCloseMessage".equals(type)) {
            this.onPlayerChatClose(payload);
        } else if ("lunarclient.apollo.packetenrichment.v1.PlayerUseItemMessage".equals(type)) {
            this.onPlayerUseItem(payload);
        } else if ("lunarclient.apollo.packetenrichment.v1.PlayerUseItemBucketMessage".equals(type)) {
            this.onPlayerUseItemBucket(payload);
        }
    }
 
    private void onPlayerHandshake(JsonObject message) {
        String checkoutSupport = message.get("embedded_checkout_support").getAsString();
 
        JsonObject minecraftVersion = message.getAsJsonObject("minecraft_version");
        String version = minecraftVersion.get("enum").getAsString();
 
        JsonObject lunarClientVersion = message.getAsJsonObject("lunar_client_version");
        String gitBranch = lunarClientVersion.get("git_branch").getAsString();
        String gitCommit = lunarClientVersion.get("git_commit").getAsString();
        String semVer = lunarClientVersion.get("semver").getAsString();
 
        for (JsonElement element : message.getAsJsonArray("installed_mods")) {
            JsonObject mod = element.getAsJsonObject();
 
            String modId = mod.get("id").getAsString();
            String displayName = mod.get("name").getAsString();
            String modVersion = mod.get("version").getAsString();
            String modType = mod.get("type").getAsString();
        }
    }
 
    private void onPlayerAttack(JsonObject message) {
        long instantiationTimeMs = JsonUtil.toJavaTimestamp(message);
 
        JsonObject targetInfo = message.getAsJsonObject("target_info");
        JsonObject attackerInfo = message.getAsJsonObject("attacker_info");
 
        this.onPlayerInfo(targetInfo);
        this.onPlayerInfo(attackerInfo);
    }
 
    private void onPlayerChatOpen(JsonObject message) {
        long instantiationTimeMs = JsonUtil.toJavaTimestamp(message);
        this.onPlayerInfo(message.getAsJsonObject("player_info"));
    }
 
    private void onPlayerChatClose(JsonObject message) {
        long instantiationTimeMs = JsonUtil.toJavaTimestamp(message);
        this.onPlayerInfo(message.getAsJsonObject("player_info"));
    }
 
    private void onPlayerUseItem(JsonObject message) {
        long instantiationTimeMs = JsonUtil.toJavaTimestamp(message);
        this.onPlayerInfo(message.getAsJsonObject("player_info"));
 
        boolean mainHand = message.get("main_hand").getAsBoolean();
    }
 
    private void onPlayerUseItemBucket(JsonObject message) {
        long instantiationTimeMs = JsonUtil.toJavaTimestamp(message);
        this.onPlayerInfo(message.getAsJsonObject("player_info"));
 
        JsonObject rayTraceResult = message.getAsJsonObject("ray_trace_result");
 
        if (rayTraceResult.has("block")) {
            JsonObject blockHit = rayTraceResult.getAsJsonObject("block");
 
            JsonObject hitLocation = blockHit.getAsJsonObject("hit_location");
            JsonObject blockLocation = blockHit.getAsJsonObject("block_location");
            String directionStr = blockHit.get("direction").getAsString();
        } else if (rayTraceResult.has("entity")) {
            JsonObject entityHit = rayTraceResult.getAsJsonObject("entity");
 
            JsonObject hitLocation = entityHit.getAsJsonObject("hit_location");
            String entityId = entityHit.get("entity_id").getAsString();
        } else {
            // MISS
        }
    }
 
    private void onPlayerInfo(JsonObject info) {
        UUID uuid = JsonUtil.toJavaUuid(info.getAsJsonObject("player_uuid"));
        Location location = JsonUtil.toBukkitPlayerLocation(info.getAsJsonObject("location"));
        boolean sneaking = info.get("sneaking").getAsBoolean();
        boolean sprinting = info.get("sprinting").getAsBoolean();
        boolean jumping = info.get("jumping").getAsBoolean();
        float forwardSpeed = info.get("forward_speed").getAsFloat();
        float strafeSpeed = info.get("strafe_speed").getAsFloat();
    }
}

Player Detection Roundtrip Packets