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1 parent 7352e02 commit 24c180a43f12a185f75648b97c9ae8f2bb658069 @mmcgill mmcgill committed Oct 22, 2011
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## What is mc3p?
mc3p (short for Minecraft Protocol-Parsing Proxy) is a Minecraft proxy
-server with a Python plugin API for reading/modifying/injecting Minecraft
-client-server messages.
+server. With mc3p, you can create programs (mc3p plugins) that examine
+and modify messages sent between the Minecraft client and server without
+writing any multi-threaded or network-related code.
-## Using mc3p to forward Minecraft connections.
+## Running mc3p.
-With no plugins configured, mc3p acts as a simple proxy. Suppose your network
-administrator only allows outbound connections on port 80, but you want to
-play Minecarft on your favorite server, If you have access
-to a computer with python and a public IP address, you can use mc3p to forward
-your connection at the expense of some extra latency.
+To start an mc3p server that listens on port 80 and forwards connections
+to a Minecraft server:
-On your server, run mc3p at the command line like so (you may need
-root/Administrator privileges, depending on your OS):
+ $ python -p 80 <server>
- $ python -p 80
- INFO|17:53:41|mc3p - mitm_listener bound to 80
-In your Minecraft client, add <yourserver>:80 to the server list and
-refresh it. You should see the server message, and be able
-to connect to through mc3p.
+Within your Minecraft client, you can then connect to <server> through
+mc3p using the server address 'localhost:80'. However, to do anything useful
+you must enable some plugins.
## Using mc3p plugins.
-If all you need is port forwarding, there are easier ways. The value of mc3p
-is its plugin API. An mc3p plugin has complete control over all the
-messages that pass between the Minecraft client and server. A plugin can
-register to intercept messages of any type, and can drop, modify, or inject
-any message at will. Best of all, mc3p does all the work of parsing the
-Minecraft protocol and handling network I/O, freeing plugin developers to
-focus on functionality.
+An mc3p plugin has complete control over all the messages that pass between
+the Minecraft client and server. By manipulating messages sent between client
+and server, you can add useful functionality without modifying client or server
+To run a plugin, you must enable it with the --plugin <name> option when you start mc3p.
+All enabled plugins are initialized after a client successfully connects to a server.
+For example, to run the plugin named 'mute':
+ $ python --plugin 'mute' <server>
+Some plugins accept arguments that modify their behavior. To pass arguments
+to a plugin, enclose them in parentheses following the plugin's name, like so:
+--plugin '<name>(<arguments>)'. Be sure to use quotes, or escape the parentheses
+as required by your shell.
-The 'mute' plugin is provided as a simple example of mc3p's flexibility,
+ $ python --plugin '<plugin>(<arguments>)' <server>
+## A Plugin Example: mute
+The 'mute' plugin is provided as a simple example of mc3p's flexibility.
This plugin allows a player to mute chat messages from selected players on a
-server. This functionality requires no modification to either the Minecraft
-client or server.
+server. It requires no modification to either the Minecraft client or server.
-We can load the plugin by starting mc3p with the --plugin command line option:
+Give it a try: start mc3p with the 'mute' plugin enabled:
- $ python --plugin mute:mute
+ $ python --plugin 'mute'
-mc3p initializes the mute plugin when the Minecraft client connects to a server
-through the proxy. We can now mute a player by entering '/mute NAME' in chat,
-unmute with '/unmute NAME', and display muted players with '/muted'. The plugin
-works by intercepting (and sometimes discarding) Minecraft chat messages.
+You can now mute a player by typing '/mute NAME' in chat,
+and unmute them with '/unmute NAME'. You can display muted players with '/muted'.
-## Writing mc3p plugins.
+The plugin works by intercepting Minecraft all chat messages, and silently
+discarding those sent by muted players.
+Now take a look at the source code for the 'mute' plugin, found in plugin/
from plugins import MC3Plugin, msghdlr
@@ -94,7 +100,53 @@ works by intercepting (and sometimes discarding) Minecraft chat messages.
# Drop messages containing the string <NAME>, where NAME is a muted player name.
return not any(txt.startswith('<%s>' % name) for name in self.muted_set)
+Every mc3p plugin (e.g. contains a single *plugin class*, a
+subclass of MC3Plugin. A plugin must contain *exactly* one plugin class;
+mc3p will print an error if multiple sub-classes of MC3Plugin are found.
+Once a client successfully connects to a server through the proxy, mc3p
+creates an instance of the plugin class of each enabled plugin, and calls its
+'init' method. Plugin classes should override 'init' to perform plugin-specific
+set-up. If the plugin was enabled with an argument string, that string is passed in
+the 'args' parameter; otherwise, 'args' is None.
+A plugin class registers a *message handler* for every message type it wishes
+to receive. To register a method of a plugin class as a message handler, decorate
+it with '@msghdlr'. the '@msghdlr' decorator takes one or more message types
+as arguments. Each message handler should take two arguments (in addition to 'self'):
+* 'msg', a dictionary representing the message, and
+* 'source', which indicates the sender of the message; source is either
+ 'client' or 'server'.
+The 'msg' dictionary always maps the key 'msgtype' to the message's type. If
+your message handler is registered for multiple types, you can determine the type
+of a given message by checking msg['msgtype']. The other key-value pairs
+in the 'msg' dictionary depend on the specific message type. See
+for a definition of the keys associated with each message type.
+A message handler returns a boolean value indicating whether the message should
+be forwarded to its destination. A return value of True forwards the message,
+while a return value of False silently drops it. The message handler may also
+modify the message by changing the values of the 'msg' dictionary, and
+returning True.
+The mute plugin registers the 'handle_chat' method as a message handler for
+messages of type '0x03', which represent chat messages. If the chat message
+is sent from the client, we check to see if it is a command to the mute plugin.
+If so, then we process it, and drop it by returning False. If not, we forward it
+by returning True. If the chat message is from the server, then we forward it
+if it was not sent by a currently blocked player.
+Along with modifying or dropping messages, a plugin can create new messages
+by passing a 'msg' dictionary with a 'msgtype' and all relevant key-value pairs
+to the 'to_client' or 'to_server methods, which are defined in the MC3Plugin class.
+The mute plugin uses the 'to_client' method to inject chat messages that indicate
+the result of each command issued by the user. Note that since these messages
+are sent to the client, and not the server, they are not visible to any other
+user on the server.
## Installation.

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