JBossAS 5.1.0 and later include a deployer for network applications which use XNIO directly.  Here's the steps for using it (this example is a TCP server).

1. Write a class that implements IoHandlerFactory<TcpChannel>.  Your application will need to depend on the XNIO API JAR which you can download from the project page.
2. Write a jboss-beans.xml file like so:

   <?xml version="1.0" encoding="UTF-8"?>
   
   <deployment xmlns="urn:jboss:bean-deployer:2.0">
       <!-- This is your class that you wrote above -->
       <bean name="MyHandlerFactory" class="com.your.handler.ClassName"/>
   
       <xnio xmlns="urn:jboss:xnio:1.0">
           <tcp-server name="MyTcpServer">
               <handler-factory-bean name="MyHandlerFactory"/>
   
               <!-- Use the command-line JBoss bind address -->
               <bind-address address="${jboss.bind.address}" port="1234"/>
           </tcp-server>
       </xnio>
   </deployment>
3. Package your JAR, including your classes in the normal place, and put the jboss-beans.xml file in the META-INF area.
4. Deploy your JAR by copying it into the deploy/ directory in your chosen server profile.

That's it!