Ignore this post if you're just doing this for fun or if you're requirements are more complex than what you've described, but....

Just from reading your requirements, I'd say that your daemon is already probably running on your server: sshd!
Read the following aloud to yourself:

I would like to do a daemon that listen in a specific port. This daemon will run commands come from client machines. I will develop a web application that will permit actions like start and stop, of several services (apache,mysql,asterisk...), so the application will connect in this daemon to run commands (/etc/init.d/mysql stop, for examplo)

Your description is exactly that of someone doing ssh <host> <command>. Of course in your case the someone will be your "web application".

If you hate security, passwords, and keys and all that then do telnet instead.