Well thanks. This did helped up to some extent. I changed the port to 8180 and ant build works fine now. Now i got to know that the error which i mentioned occurs if i start tomcat from eclipse. Neveetheless,I learnt about the other exception which occurs when port is 80. Let me explain it below
1) With port "80" and if i start tomcat from outside(not from eclipse), then i get below error if i execute "ant list"
Now i changed the port to 8180, do an ant build and it works absolutely fine.
But if i start tomcat from eclipse (even with new port 8180) ,and do an ant build, then still i get the same old exception which i mentioned in previous post
Someone says "Impossible is nothing". The man next him says "Let me see you licking your elbow tip!"
found a solution. the problem is like I said the webapps-folder within the workspace and the missing manager app. you need to add the folowing line to the server.xml in your workspaces server/tomcat folder