Open %JBOSS_HOME%\server\default\deploy\jboss-web.deployer\server.xml and change the port as per your requirement.
<Connector port="8081" address="0.0.0.0" maxThreads="250" maxHttpHeaderSize="8192"
emptySessionPath="true" protocol="HTTP/1.1"
enableLookups="false" redirectPort="8443" acceptCount="100"
connectionTimeout="20000" disableUploadTimeout="true" />