ProtocolLib/Readme.md

ProtocolLib 
===========

Certain tasks are impossible to perform with the standard Bukkit API, and may require 
working with and even modify Minecraft directly. A common technique is to modify incoming 
and outgoing [packets](http://www.wiki.vg/Protocol), or inject custom packets into the
stream. This is quite cumbersome to do, however, and most implementations will break 
as soon as a new version of Minecraft has been released, mostly due to obfuscation.

Critically, different plugins that use this approach may _hook_ into the same classes, 
with unpredictable outcomes. More than often this causes plugins to crash, but it may also 
lead to more subtle bugs.

Currently maintained by dmulloy2 on behalf of [SpigotMC](http://www.spigotmc.org/)


### Resources

* [Downloads](http://ci.shadowvolt.com/job/ProtocolLib)
* [JavaDoc](http://ci.shadowvolt.com/job/ProtocolLib/javadoc)


Building
--------
You can compile this project yourself by using the latest version of Maven.


A new API
---------

__ProtocolLib__ attempts to solve this problem by providing a event API, much like Bukkit, 
that allow plugins to monitor, modify or cancel packets sent and received. But more importantly, 
the API also hides all the gritty, obfuscated classes with a simple index based read/write system. 
You no longer have to reference CraftBukkit!


### Using ProtocolLib

To use the library, first add ProtocolLib.jar to your Java build path. Then, add ProtocolLib
as a dependency (or soft-dependency, if you can live without it) to your plugin.yml file:

````yml
depends: [ProtocolLib]
````

Future versions will be available in a public Maven repository, possibly on Maven central. But it
will always be possible to reference ProtocolLib manually.

Then get a reference to ProtocolManager in onLoad() and you're good to go.

````java
private ProtocolManager protocolManager;

public void onLoad() {
    protocolManager = ProtocolLibrary.getProtocolManager();
}
````

To listen for packets sent by the server to a client, add a server-side listener:

````java
// Disable all sound effects
protocolManager.addPacketListener(
  new PacketAdapter(this, ListenerPriority.NORMAL, 
          PacketType.Play.Server.NAMED_SOUND_EFFECT) {
    @Override
    public void onPacketSending(PacketEvent event) {
        // Item packets (id: 0x29)
        if (event.getPacketType() == 
                PacketType.Play.Server.NAMED_SOUND_EFFECT) {
            event.setCancelled(true);
        }
    }
});
````

It's also possible to read and modify the content of these packets. For instance, you can create a global
censor by listening for Packet3Chat events:

````java
// Censor
protocolManager.addPacketListener(new PacketAdapter(this,
        ListenerPriority.NORMAL, 
        PacketType.Play.Client.CHAT) {
    @Override
    public void onPacketReceiving(PacketEvent event) {
        if (event.getPacketType() == PacketType.Play.Client.CHAT) {
            PacketContainer packet = event.getPacket();
            String message = packet.getStrings().read(0);

            if (message.contains("shit")
                    || message.contains("damn")) {
                event.setCancelled(true);
                event.getPlayer().sendMessage("Bad manners!");
            }
        }
    }
});
````

### Sending packets

Normally, you might have to do something ugly like the following:

````java
Packet60Explosion fakeExplosion = new Packet60Explosion();
	
fakeExplosion.a = player.getLocation().getX();
fakeExplosion.b = player.getLocation().getY();
fakeExplosion.c = player.getLocation().getZ();
fakeExplosion.d = 3.0F;
fakeExplosion.e = new ArrayList<Object>();

((CraftPlayer) player).getHandle().netServerHandler.sendPacket(fakeExplosion);
````

But with ProtocolLib, you can turn that into something more manageable. Notice that 
you don't have to create an ArrayList with this version:

````java

fakeExplosion.getDoubles().
    write(0, player.getLocation().getX()).
    write(1, player.getLocation().getY()).
    write(2, player.getLocation().getZ());
fakeExplosion.getFloat().write(0, 3.0F);

try {
    protocolManager.sendServerPacket(player, fakeExplosion);
} catch (InvocationTargetException e) {
    throw new RuntimeException(
        "Cannot send packet " + fakeExplosion, e);
}
````

Compatiblity
------------

One of the main goals of this project was to achieve maximum compatibility with CraftBukkit. And the end
result is quite flexible - in tests I successfully ran an unmodified ProtocolLib on CraftBukkit 1.8.0, and
it should be resiliant against future changes. It's likely that I won't have to update ProtocolLib for
anything but bug and performance fixes. 

How is this possible? It all comes down to reflection in the end. Essentially, no name is hard coded - 
every field, method and class is deduced by looking at field types, package names or parameter
types. It's remarkably consistent across different versions.


### Incompatiblity

The following plugins (to be expanded) are not compatible with ProtocolLib: