Some times new version of tomcat not starts at default port usually 8080. Reason behind this another version of tomcat installed and it starts when OS starts. We can resolve this problem by removing older version of tomcat OR stopping auto start tomcat at default port.
We can remove tomcat using terminal in Ubuntu with these very simple steps:
Step 1: Find all packages related with tomcat
dpkg -l|grep tomcat
Step 2: Remove desired tomcat package
sudo dpkg -P (package you want to delete)
if your desired package is tomcat6 then type sudo dpkg -P tomcat6
→ Now tomcat installation removed from Ubuntu and 8080 port is free.