Seems your port is being used. If you don't have lsof already you can download and install it by becoming root and running:
root@machine:~# apt-get install lsof
To discover the process name, ID (pid), and other details you need to run:
lsof -i :port
So to see which process is listening upon port 24 we can run:
root@machine:~# lsof -i :24
After this you should be able to move on towards a solution.