Determining Available Ports on a Linux Machine

I want to determine which ports are available on a Linux machine.  I assume there might be a command to do that?  If so what is it?
onaled777Asked:
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Gerwin Jansen, EE MVETopic Advisor Commented:
Do you mean tcp ports above port 1000 that you can use to start a server on for example?

You can do this:

netstat -a | grep -i listen

This will show you the ports that are used (LISTENed) to. Other ports are available.

What is it you want to do?
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onaled777Author Commented:
I need to know if server ports are open and accessible. Is there a command that I can provide a port number to in order to determine if it is open? If not I will work with what you provided above.
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Gerwin Jansen, EE MVETopic Advisor Commented:
You could use nc (netcat) for that, like this (checking port 9090):

nc -ul 9090

If you don't get the ... already in use ... message then the port is free.
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