Table of Contents
The most important thing to understand is that Tigase is very modular and you can have multiple components running inside single instance. However one of the most important components is MessageRouter, which sits in the centre and serves as a, as name suggest, packet router directing packets to the appropriate components.
There is also a group of specialised component responsible for handling users connections:
bosh). They receive packets from the incoming connection, then subsequently they forward processed packet to
MessageRouter. Most of the time, especially for packets coming from user connections, packet is routed to
SessionManager component (with the session object referring to appropriate user in case of client to server connection). After processing in
SessionManager packet goes back to
MessageRouter and then, based on the stanza addressing` can go to different component (muc, pubsub) or if it’s addressed to another user it can go through:
MessageRouterand then (user)
s2s(server to server connection manager) if the user or component is on the different, federated, xmpp server;
In a very broad view this can be depicted with a following graph:
To make it easier to get into the code below are defined basic terms in the Tigase server world and there is a brief explanation how the server is designed and implemented. This document also points you to basic interfaces and implementations which can be used as example code reference.
Logically all server code can be divided into 3 kinds of modules: components, plug-ins and connectors.
There is an API defined for each kind of above modules and all you have to do is enable the implementation of that specific interface. Then the module can be loaded to the server based on it’s configuration settings. There is also abstract classes available, implementing these interfaces to make development easier.
Here is a brief list of all interfaces to look at and for more details you have to refer to the guide for specific kind of module.
This is list of interfaces to look at when you work on a new component:
ServerComponentand is required to implement by components which want to receive data packets like session manager and c2s connection manager.
Instead of implementing above interfaces directly, it is recommended to extend one of existing abstract classes which take care of the most of "dirty and boring" stuff. Here is a list the most useful abstract classes:
tigase.server.AbstractMessageReceiver - Implements 4 basic interfaces:
StatisticsContainer. AbstractMessageReceiver also manages internal data queues using it’s own threads which prevents dead-locks from resource starvation. It offers even-driven data processing which means whenever packet arrives the
abstract void processPacket(Packet packet); method is called to process it. You have to implement this abstract method in your component, if your component wants to send a packet (in response to data it received for example).
boolean addOutPacket(Packet packet)
tigase.server.ConnectionManager - This is an extension of
AbstractMessageReceiver abstract class. As the name says this class takes care of all network connection management stuff. If your component needs to send and receive data directly from the network (like c2s connection, s2s connection or external component) you should use this implementation as a basic class. It takes care of all things related to networking, I/O, reconnecting, listening on socket, connecting and so on. If you extend this class you have to expect data coming from to sources:
MessageRouter and this is when the
abstract void processPacket(Packet packet); method is called and second, from network connection and then the
abstract Queue processSocketData(XMPPIOService serv); method is called.
All Tigase plugins currently implemented are located in package: tigase.xmpp.impl. You can use this code as a sample code base. There are 3 types of plug-ins and they are defined in interfaces located in
Data received from the network are read from the network sockets as bytes by code in the
tigase.io package. Bytes then are changed into characters in classes of
tigase.net package and as characters they are sent to the XML parser (
tigase.xml) which turns them to XML DOM structures.
All data inside the server is exchanged in XML DOM form as this is the format used by XMPP protocol. For basic XML data processing (parsing characters stream, building DOM, manipulate XML elements and attributes) we use Tigase XML parser and DOM builder.
Each stanza is stored in the
tigase.xml.Element object. Every Element can contain any number of Child Elements and any number of attributes. You can access all these data through the class API.
To simplify some, most common operations Element is wrapped in
tigase.server.Packet class which offers another level of API for the most common operations like preparation of response stanza based on the element it contains (swap to/from values, put type=result attribute and others).