| msgType | The message type of the handler to use. | 
| reader | The stream to read the contents of the message from. | 
| channelId | The channel that the message arrived on. | 
| netMsg | The message object to process. | 
bool True if a handler function was found and invoked.
This function invokes the registered handler function for a message.
Network connections used by the NetworkClient and NetworkServer use this function for handling network messages.