If you have enabled Docker Remote API, per Enable Docker Remote API, you may be vulnerable to attacks.

Information Gathering & Enumeration

sudo nmap -sS -T5 192.168.1.118 -p-Starting Nmap 7.01 ( https://nmap.org ) at 2017-04-11 12:37 CEST
Nmap scan report for 192.168.1.118
Host is up (0.00076s latency).
Not shown: 65498 closed ports, 35 filtered ports
PORT     STATE SERVICE
22/tcp   open  ssh
1234/tcp open  docker
MAC Address: 0C:01:67:8A:63:F2 (Oracle VirtualBox virtual NIC)

I had to scan more ports that the default top 1000 because the docker API port is not included :( Ok then, what about service detection?

nmap -sTV -p 2376 192.168.1.7Starting Nmap 7.01 ( https://nmap.org ) at 2018-08-10 16:35 CEST Nmap scan report for 192.168.1.7 Host is up (0.00038s latency). PORT STATE SERVICE VERSION 2376/tcp open 18.06.0-ce DockerService detection performed. Please report any incorrect results at https://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 77.78 seconds

This confirm that we are dealing with Docker, nmap also discovered the exact version of Docker, if we want to confirm it manyally we can issue a GET request to the endpoint located at: http:<IP>:2376/version