Tomcat occupies 4 ports while running, if multi tomcat instances run on a same OS, the ports of each tomcat should be change to avoid port conflict. Here's brief of the 4 ports:

1. Port for shutdown：
<Server port="8005" shutdown="SHUTDOWN">

2. HTTP port：
<Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />