I do odd jobs from my home office. It’s not much but it supports my hobbies. Recently I was handed a POS and asked to configure it/integrate a new PinPad from a vendor that was not already supported.The first task was to login. It was a linux based system with an ethernet port and ssh-server running. When the machine boots up it calls for an IP address from the local DHCP server. In my case the DHCP is served by my firewall. Depending on the type of software running on the DHCP server sometimes they list the IP address leases. This one did not.nmap is a tool used to locate hosts and open ports. It has a number of good and bad uses.The first step is to install nmap. This is simple on most Linux distros. Since the system I’m on is OSX I had an extra step. Assuming that I already macports already installed.sudo port install nmapOnce the installation was completed I needed to execute the search.nmap -v -p22 10.0.1.2-200"-v" is the option for verbose"-p22" is the setting to search for port 22 on each IP address. (port 22 is the ssh server port in most configurations)“10.0.1.2-200” tells nmap to search the 199 IP address from 10.0.1.2 thru 10.0.1.200… for example: 10.0.1.2, 10.0.1.3, 10.0.1.4 … and so on.I got my list of devices and since it was a short list it was easy enough to try each.Initiating Connect Scan at 19:10Scanning 10 hosts [1 port/host]Discovered open port 22/tcp on 10.0.1.27Discovered open port 22/tcp on 10.0.1.21Completed Connect Scan at 19:10, 0.20s elapsed (10 total ports)Nmap scan report for 10.0.1.5Host is up (0.19s latency).PORT STATE SERVICE22/tcp closed sshNmap scan report for 10.0.1.20Host is up (0.023s latency).PORT STATE SERVICE22/tcp closed sshNmap scan report for 10.0.1.21Host is up (0.0028s latency).PORT STATE SERVICE22/tcp open sshNmap scan report for 10.0.1.22Host is up (0.0061s latency).PORT STATE SERVICE22/tcp closed sshNmap scan report for 10.0.1.23Host is up (0.00027s latency).PORT STATE SERVICE22/tcp closed sshNmap scan report for 10.0.1.24Host is up (0.0028s latency).PORT STATE SERVICE22/tcp closed sshNmap scan report for 10.0.1.25Host is up (0.20s latency).PORT STATE SERVICE22/tcp closed sshNmap scan report for 10.0.1.27Host is up (0.0025s latency).PORT STATE SERVICE22/tcp open sshNmap scan report for 10.0.1.28Host is up (0.0063s latency).PORT STATE SERVICE22/tcp filtered sshNmap scan report for 10.0.1.29Host is up (0.0062s latency).PORT STATE SERVICE22/tcp filtered sshRead data files from: /opt/local/share/nmapNmap done: 199 IP addresses (10 hosts up) scanned in 20.18 seconds