Currently i am not using Tomcat inside JBOSS
Actually, JBoss AS comes with a version of Tomcat (known as JBoss Web) embedded within it - JBoss Web handles HTTP requests. So yes, JBoss Web would be used to access the console.
Also i want to know by editing which file can i change the listening port
See
http://community.jboss.org/wiki/AS5ServiceBindingManager
Also i want to know the prerequesties to acess web console/
Which "web console"? I ask because I am not sure which console you mean. JBoss AS 4.2.3 has several "consoles":
http://localhost:8080 - this is the home page
http://localhost:8080/web-console - this is the "web console," but it is old, out-of-date and no longer updated. In many cases it does not even work.
http://localhost:8080/jmx-console - the "jmx console" provides access to the deployed MBeans
http://localhost:8080/admin-console - starting with JBoss AS 5 this is the new admin console
As far as prerequisites go, the only one is to start JBoss AS.