sudo apt-get install arp-scan

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

brew install arp-scan

#!/bin/sh

DEBUG=false # Enable debug output
STATUSURL_CONNECTED="https://www.divera247.com/statusgeber.html?status=1&accesskey=..." # Replace with your personal status url if connected
STATUSURL_DISCONNECTED="https://www.divera247.com/statusgeber.html?status=2&accesskey=..." # Replace with your personal status url if disconnected

HOSTNAME="divera247-phone" # Use `arp -a` to get your devicename
NETWORK_INTERFACE="en0" # Use `ifconfig` to get you connected network adapter

CONNECTED=true # Initial state
ACK_THRESHOLD=2 # Minimum times device must not be reachable to be marked as disconnected
ACK_COUNTER=0 # Number of times device did not acknowledge

function connectionStateToggled {
  if [ "$CONNECTED" = true ]; then
    echo "$HOSTNAME connected"

    # Set connected status
    CURL_OUTPUT=$(curl --silent -w "\n\nStatus Code: %{http_code}\n\n" "$STATUSURL_CONNECTED" 2>&1)
    STATUS_CODE=$(echo "$CURL_OUTPUT" | grep "Status Code")

    # Print server output in error case
    if [ $DEBUG = true ] || [[ "$STATUS_CODE" != *"200"* ]]; then
      echo "$CURL_OUTPUT"
    fi
  else
    echo "$HOSTNAME disconnected"

    # Set disconnected status
    CURL_OUTPUT=$(curl --silent -w "\n\nStatus Code: %{http_code}\n\n" "$STATUSURL_DISCONNECTED" 2>&1)
    STATUS_CODE=$(echo "$CURL_OUTPUT" | grep "Status Code")

    # Print server output in error case
    if [ $DEBUG = true ] || [[ "$STATUS_CODE" != *"200"* ]]; then
      echo "$CURL_OUTPUT"
    fi
  fi
}

while true; do
  HOSTNAMES_FROM_ROUTER=$(arp -a)

  # Check if device is in cached list and get IP address from it
  IP_OF_DEVICE=$(echo "$HOSTNAMES_FROM_ROUTER" | grep $HOSTNAME | awk -F '[()]' '{print $(NF-1)}')

  if [[ ! -z $IP_OF_DEVICE ]]; then
    # Scan network to check if device is really still connected
    NETWORKSCAN=$(arp-scan --interface=$NETWORK_INTERFACE --localnet)

    if [[ "$NETWORKSCAN" == *"$IP_OF_DEVICE"* ]]; then
      $DEBUG && echo "Found $HOSTNAME as $IP_OF_DEVICE in network scan"

      # Device is reachable by network scanner
      # If previously have been connected, set status at home
      if [ "$CONNECTED" = false ]; then
        CONNECTED=true
        ACK_COUNTER=0
        connectionStateToggled
      fi
    else
      $DEBUG && echo "$HOSTNAME did not respond to network scan"

      # Device is not reachable by network scanner
      ACK_COUNTER=$((ACK_COUNTER + 1))

      # If device didn't respond ACK_THRESHOLD times: set status or ignore
      if (( ACK_COUNTER >= ACK_THRESHOLD )) && [ "$CONNECTED" = true ]; then
        CONNECTED=false
        connectionStateToggled
      fi
    fi
  else
    $DEBUG && echo "$HOSTNAME wasn't found in routers list of known devices"

    # Device is not in cached list, so it has been disconnected a while ago
    ACK_COUNTER=$((ACK_COUNTER + 1))


    if (( ACK_COUNTER >= ACK_THRESHOLD )) && [ "$CONNECTED" = true ]; then
      CONNECTED=false
      connectionStateToggled
    fi
  fi


  # Wait some time before next iteration, otherwise devices could not respond to scan
  sleep 15

done