port being in use not displayed in netstat output

In what scenarios port being used by a process don't show up in netstat -a output? I'm running jenkins on my machine. It's listening on port 8080. I'm trying to start another process that tries to bind on same port and it fails with error that port is already in use. Now when I do netstat -a | grep 8080, it doesn't show up in output. After stopping jenkins my process successfully bound to 8080. Any clues what happening? I'm running CentOS.