Why is it not being scanned with nmap?

Question

Burglary protection

Began to deal with the security tools built into Parrot OS. I have a second PC, I'm doing my experiments on it :) I want to scan it for open ports via nmap. The output is
┌─[[email protected]]─[/home/***]
└──╼ #nmap xx.xxx.xx.xxx
Starting Nmap 7.01 ( https://nmap.org ) at 2016-05-02 17:44 YEKT
mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled. Try using --system-dns or specify valid servers with --dns-servers
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.09 seconds

Answer 1

nmap writes - the preliminary ping did not pass, it considers the host turned off and not worthy of attention. If you are sure that this is not the case, turn off the pre-check mode. ( -Pn )
If it still doesn't output any results after that, the first 1024 ports it scans by default may be blocked by a firewall. In order to understand what exactly and in what sequence nmap did - use the -v
switch . In general, nmap has many different scanning modes, using different protocols.
If for some reason you are not satisfied with the built-in man - here is a good translation

Answer 2

nmap tells you exactly what happened and what to do.
Learn technical English, without it in our business - "nowhere, nowhere, no way"