how to check if port is open and unused

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http://stackoverflow.com – I want to install webserver-apache on a Linux platform which uses port no.80 but I am not sure whether is port is open or not , and being used by some other application or not. Output of grep 80 /etc/services is: http 80/tcp www www-http #World Wide web Http http 80/udp www www-http #Hypertext transfer protocol 2."netstat -an | grep 80 | more" : It gives some IP's one of which is IP:80 TIME_WAIT Could you please help and tell how can i find out if port 80 is open and unused so that I can start installation. (HowTos)