gistfile1.java

public static void sendUpdateToAllTrackers(Entity tag, Packet packet) {
        final World w = tag.worldObj;
        Preconditions.checkArgument(w instanceof WorldServer, "This method can only be executed on server side");
        WorldServer server = (WorldServer)w;
        server.getEntityTracker().sendPacketToAllPlayersTrackingEntity(tag, packet);
}

public static void sendPacketToWatchers(WorldServer server, int x, int z, Packet packet) {
    int chunkX = x >> 4;
    int chunkZ = z >> 4;

    try {
        // wrongly named, PlayerInstance is in fact chunk watchers list
        PlayerInstance playerInstance = server.getPlayerManager().getOrCreateChunkWatcher(chunkX, chunkZ, false);
        if (playerInstance != null)
            playerInstance.sendToAllPlayersWatchingChunk(packet);
    } catch (Exception e) {
      Throwables.propagate(throwable)
    }
}