The Minecraft Protocol Parsing Proxy (with Plugin support! and alliteration!)
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What is mc3p?

mc3p (short for Minecraft Protocol-Parsing Proxy) is a Minecraft proxy 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.

Installing from source

To install from source, just clone the GitHub repository. You can then run mc3p directly from the top-level directory of the repository, or install it in 'development' mode with

python develop

If mc3p is installed in 'development' mode, you can uninstall it with

python develop --uninstall


Linux / Mac OS X


Running mc3p.

To start an mc3p server that listens on port 25566 and forwards connections to a Minecraft server:

$ python -m mc3p.proxy -p 25566 <server>

Within your Minecraft client, you can then connect to through mc3p using the server address 'localhost:25566'. However, to do anything useful you must enable some plugins.

Using mc3p plugins.

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 code.

To run a plugin, you must enable it with the --plugin option when you start mc3p. All enabled plugins are initialized after a client successfully connects to a server. For example, to run the mute example plugin that comes with mc3p:

$ python -m mc3p.proxy --plugin 'mc3p.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 '()'. Be sure to use quotes, or escape the parentheses as required by your shell.

$ python -m mc3p.proxy --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. It requires no modification to either the Minecraft client or server.

Give it a try: start mc3p with the 'mute' plugin enabled:

$ python -m mc3p.proxy --plugin 'mc3p.plugin.mute'

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'.

The plugin works by intercepting all Minecraft chat messages, and silently discarding those sent by muted players.

Now take a look at the source code for the 'mute' plugin:

from mc3p.plugins import MC3Plugin, msghdlr

class MutePlugin(MC3Plugin):
    """Lets the client mute players, hiding their chat messages.

    The client controls the plugin with chat commands:
        /mute NAME      Hide all messages from player NAME.
        /unmute NAME    Allow messages from player NAME.
        /muted          Show the list of currently muted players.
    def init(self, args):
        self.muted_set = set() # Set of muted player names.

    def send_chat(self, chat_msg):
        """Send a chat message to the client."""
        self.to_client({'msgtype': 0x03, 'chat_msg': chat_msg})

    def mute(self, player_name):
        self.send_chat('Muted %s' % player_name)

    def unmute(self, player_name):
        if player_name in self.muted_set:
            self.send_chat('Unmuted %s' % player_name)
            self.send_chat('%s is not muted' % player_name)

    def muted(self):
        self.send_chat('Currently muted: %s' % ', '.join(self.muted_set))

    def handle_chat(self, msg, source):
        txt = msg['chat_msg']
        if source == 'client':
            # Handle mute commands
            if txt.startswith('/mute '):     self.mute(txt[len('/mute '):])
            elif txt.startswith('/unmute '): self.unmute(txt[len('/unmute '):])
            elif txt == '/muted':            self.muted()
            else: return True # Forward all other chat messages.

            return False # Drop mute plugin commands.
            # 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 is a Python module that 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, a number between 0 and 0xFF. 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.