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find open ports in linux

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List open ports

Using Netstat Command

The flag -l tells netstat to print all listening sockets, -t shows all TCP connections, -u displays all UDP connections and -p enables printing of application/program name listening on the port.

To print numeric values rather than service names, add the -n flag.

netstat -ltup


Using ss Command

ss -lntu




Using Nmap Command

Installation

apt install nmap [On Debian/Ubuntu]

yum install nmap [On CentOS/RHEL]

dnf install nmap [On Fedora 22+]

Usage

nmap -n -PN -sT -sU -p- localhost




Using lsof Command

To list all Internet and network files, use the -i option. Note that this command shows a mix of service names and numeric ports.

lsof -i

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