<p>Smack is a library for client-to-server XMPP connections to perform real-time communications and data exchange. This includes, but is not limited to, instant messaging and group chat. More generically speaking, it allows you to easily exchange data in various ways: For example fire-and-forget, publish-subscribe, between human and non-human endpoints. The use cases include M2M, IoT, and many more.</p>
<p>Smack is a pure Java library, open-source and highly modular. It runs on Android and Java SE. The API strives to be easy to use but yet powerful.</p>
<p>Smack doesn't force you to code at the protcol level of XMPP. The library provides intelligent higher level constructs, often called {@link org.jivesoftware.smack.Manager}, which let you program more efficiently. Other examples of those constructs are the Chat and Roster classes.</p>
<p>Smack comes with APIs for easy machine-to-machine communication. You can set any number of properties on each message, including properties that are Java objects.</p>
<p>XMPP (eXtensible Messaging and Presence Protocol) is an open protocol standardized by the <ahref="https://ietf.org/">Internet Engineering Task Force (IETF)</a> and supported and extended by the <ahref="https://www.xmpp.org/">XMPP Standards Foundation (XSF)</a>.</p>
<p>Smack is meant to be easily embedded into any existing Java
application. The library ships as several modules to provide more
flexibility over which features applications require.</p>
<ul>
<li>smack-core -- provides core XMPP functionality. All XMPP features that are part of the XMPP RFCs are included.</li>
<li>smack-im -- provides functionality defined in RFC 6121 (XMPP-IM), like the Roster.</li>
<li>{@link org.jivesoftware.smack.tcp smack-tcp} -- support for XMPP over TCP. Includes XMPPTCPConnection class, which you usually want to use</li>
<li>smack-extensions -- support for many of the extensions (XEPs) defined by the XMPP Standards Foundation, including multi-user chat, file transfer, user search, etc. The extensions are documented in the [extensions manual](extensions/index.md).</li>
<li>smack-experimental -- support for experimental extensions (XEPs) defined by the XMPP Standards Foundation. The API and functionality of those extensions should be considered as unstable.</li>
<li>smack-legacy -- support for legacy extensions (XEPs) defined by the XMPP Standards Foundation.
<li>smack-bosh -- support for BOSH (XEP-0124). This code should be considered as beta.</li>
<li>smack-resolver-minidns -- support for resolving DNS SRV records with the help of <ahref="https://minidns.org">MiniDNS</a>. Ideal for platforms that do not support the javax.naming API. Also supports [DNSSEC](dnssec.md) TODO: Fix link.</li>
<li>smack-resolver-dnsjava -- support for resolving DNS SRV records with the help of dnsjava.</li>
<li>smack-resolver-javax -- support for resolving DNS SRV records with the javax namespace API.</li>
<li>smack-debug -- an enhanced GUI debugger for protocol traffic. It will automatically be used when found in the classpath and when [debugging](debugging.md) is enabled.</li>
<p>Smack has an initialization process that involves 2 phases.</p>
<ul>
<li>Initializing system properties - Initializing all the system properties accessible through the class **SmackConfiguration**. These properties are retrieved by the _getXXX_ methods on that class.</li>
<li>Initializing startup classes - Initializing any classes meant to be active at startup by instantiating the class, and then calling the _initialize_ method on that class if it extends **SmackInitializer**. If it does not extend this interface, then initialization will have to take place in a static block of code which is automatically executed when the class is loaded.</li>
</ul>
<p>
Initialization is accomplished via a configuration file.
By default, Smack
will load the one embedded in the Smack jar at _org.jivesoftware.smack/smack-
config.xml_.
This particular configuration contains a list of initializer
classes to load.
All manager type classes that need to be initialized are