The default port configuration is stored in the webhcat-site.xml file. To change the default port, you will have to make changes in this file. In the webhcat-site.xml file, change the port  50111 with the port that you want to be the default port. 
<configuration>
  <property>
    <name>templeton.port</name>
    <value>50111</value>
    <description>The HTTP port for the main server.</description>
  </property>
</configuration>