Docker port checker

#!/bin/bash

# Usage: test_docker.sh <port> <sleepfor>

# Get parameters from the arguments passed
port=$1
sleepfor=$2

# Check if no argments has been passed to script
if [ "$#" -le "0" ]; then
    echo Not enough parameters passed.
    echo
    echo Usage:
    echo "test_docker.sh <port> <sleepfor>"
    exit
fi

# If the second argument hasn't been passed - set the sleep value to a default value
if [ "$sleepfor" = "" ]; then
    echo "Setting the default value for sleepfor to 1 second"
    sleepfor=1
fi

# CentOS/RedHat: yum install nc
# Fedora 22+: dmf install nc
# Ubuntu: sudo apt-get install netcat
# nc -zv localhost $port

# Begin the loop
while [ true ]
do
    # Running the port test command
    nc -zv localhost $port &> /dev/null

    # Check for errorlevel. 0 - command returned good value, >0 - not good (probably Docker is not present on this port)
    if [ "$?" -eq "1" ]; then
        echo Docker is not running on this port. Retrying...
        sleep $sleepfor

        # Do another loop, do not proceed to a restart containers routine
        continue
    fi

    echo Something is running on this port.
    sleep $sleepfor

    # TODO: Restart containers here:
    #docker restart ...

    # Get out of the loop
    break
done

echo Docker containers has been restarted