Scanning helps one to know what services are running on a machine. This will show the open ports on which services are listening for connections. First we will determine whether the target machine is alive or not. This can be done by sending a icmp echo request packet to the server. The server would respond with a icmp echo reply showing that it's alive. The process to do this on a range of hosts or ipaddresses is known as ping sweep. Of the many methods used, we will look on ICMP ping and echo port ping.
Your machine will send an icmp echo request (type 8) to the target machine and it would respond with an icmp echo reply(type 0) if it is alive. You can use the Unix ping command to do this:
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