WiFiMon Hardware Probes (WHP) are used to gather performance measurements in a WiFi network from dedicated small form factor devices which are installed in fixed points. WiFiMon tested its operation and recommends the use of Raspberry Pi’s v3 Model B+ or v4.  WiFiMon Hardware Probe will work in the following configuration:

Setting up the WHP

There are two options for the WHP installation:

  1. Installation and configuration from the prepared WiFiMon WHP image (Installation option 1)
  2. Installation and configuration on the Raspberry Pi with already installed Raspberry Pi OS (Stretch or later) (Installation option 2)

Installation and configuration

The following steps apply for both installation options. WiFiMon users who will use the prepared WHP image (installation option 1) should simply edit the crontab and wireless.py files as discussed in the following. WiFiMon users who will not use the prepared WIFiMon WHP image (installation option 2) should follow the steps 2 up to 4.

Step 1: Write the image to the micro SD card

Follow the instructions at the official Raspberry Pi site. Skip the "Download the image" step and use the WiFiMon Raspberry Pi operating system image instead (download size is approx. 8 GB).

WiFiMon Raspberry Pi image given above is a custom version of Raspberry Pi OS (Buster) with desktop, with the default Raspberry Pi credentials (user: pi, password: raspberry).

We advise the user to always secure Raspberry Pi by changing the default password.

Step 2: Start the Raspberry Pi

Follow the simple steps below:

  • Insert the microSD in the Raspberry Pi
  • Plug the USB keyboard into one of the USB ports (or USB wireless adapter for keyboard and mouse)
  • Plug the USB mouse into one of the USB ports
  • Connect the monitor cable to the Pi's HDMI port
  • Plug the power supply into a socket and connect it to the micro USB power port

You should see a red light on the Raspberry Pi and raspberries on the monitor. The WiFiMon Hardware Probe will boot up into a graphical desktop.

Step 3: Configure the Raspberry Pi


Secure the Raspberry Pi by changing the default password. Optionally, you may enable SSH to access the command line of a Raspberry Pi remotely or setup remote desktop. Next, you have to connect to the wireless network you want to measure.

First, the following programs should be downloaded:

sudo apt-get update
sudo apt-get install -y xvfb firefox-esr

The WiFiMon Hardware Probe (WHP) performs performance tests towards the WiFiMon Test Server (WTS) in an automated manner. It uses crontab to schedule the tests. To do that, open the terminal (as user "pi") and enter the command: crontab -e. You will have to pick the text editor. Then scroll to the bottom of the file and add the following code block (which you will modify as explained below): 

00,10,20,30,40,50 * * * * Xvfb :100 &
02,12,22,32,42,52 * * * * export DISPLAY=:100 && firefox-esr --new-tab URL_TO_nettest.html >/dev/null 2>&1
04,14,24,34,44,54 * * * * export DISPLAY=:100 && firefox-esr --new-tab URL_TO_speedworker.html >/dev/null 2>&1
06,16,26,36,46,56 * * * * export DISPLAY=:100 && firefox-esr --new-tab URL_TO_boomerang.html >/dev/null 2>&1
08,18,28,38,48,58 * * * * /home/pi/wireless.py >> ~/cron.log 2>&1

You have to modify the following parts of the crontab in lines 2-4:

  • URL_TO_nettest
  • URL_TO_speedworker
  • URL_TO_boomerang

You should put the URL or IP address of the WTS in which the NetTest, speedtest and boomerang JS scripts are injected. Details about the configuration of the WiFiMon testtools are included in the WiFiMon Test Server (WTS) installation documentation. Following the assumptions/notations of the WTS guide, examples of the URLs for NetTest, speedtest and boomerang respectively are (i) https://WTS_FQDN/wifimon/measurements/nettest.html, (ii) https://WTS_FQDN/wifimon/measurements/speedworker.html and (iii) https://WTS_FQDN/wifimon/measurements/boomerang.html.

Line 5 of the crontab is related to the streaming of wireless network interface metrics to the WiFiMon Analysis Server (WAS). Optionally, the intervals of the WHP measurements could be altered by appropriately configuring the crontab so that measurement are more or less frequent. The configuration of the crontab config given above sets up 10-minute intervals between the measurements of each test tool in a way in which there are no overlapping measurements.

Step 4: Streaming Wireless Network Interface Metrics to the WiFiMon Analysis Server (WAS)

In /home/pi, you will find the Python script wireless.py. The contents of the script are the following:

wireless.py
#!/usr/bin/python3

import subprocess
import datetime
import requests
from requests.packages.urllib3.exceptions import InsecureRequestWarning
requests.packages.urllib3.disable_warnings(InsecureRequestWarning)
import json

def return_command_output(command):
    proc = subprocess.Popen(command, stdout = subprocess.PIPE, shell = True)
    (out, err) = proc.communicate()
    output = out.rstrip('\n'.encode('utf8'))
    return output

def get_mac(iface):
    command = "cat /sys/class/net/" + str(iface) + "/address"
    mac = return_command_output(command).decode('utf8')
    mac = mac.replace(":", "-")
    return mac

def find_wlan_iface_name():
    command = "printf '%s\n' /sys/class/net/*/wireless | awk -F'/' '{print $5 }'"
    wlan_iface_name = return_command_output(command)
    return wlan_iface_name.decode('utf8')

def parse_iwconfig(iface):
    bit_rate = return_command_output("sudo iwconfig " + iface + " | grep Bit | awk '{print $2}' | sed 's/Rate=//'").decode('utf8')
    tx_power = return_command_output("sudo iwconfig " + iface + " | grep Bit | awk '{print $4}' | sed 's/Tx-Power=//'").decode('utf8')
    link_quality = return_command_output("sudo iwconfig " + iface + " | grep Link | awk '{print $2}' | sed 's/Quality=//'").decode('utf8')
    link_quality = link_quality.split("/")[0]
    signal_level = return_command_output("sudo iwconfig " + iface + " | grep Link | awk '{print $4}' | sed 's/level=//'").decode('utf8')
    accesspoint = return_command_output("sudo iwconfig " + iface + " | grep Mode | awk '{print $6}' | sed 's/Point: //'").decode('utf8')
    accesspoint = accesspoint.replace(":", "-")
    essid = return_command_output("sudo iwconfig " + iface + " | grep ESSID | awk '{print $4}' | sed 's/ESSID://'").decode('utf8')
    essid = essid.replace("\"", "")
    return bit_rate, tx_power, link_quality, signal_level, accesspoint, essid

def parse_iwlist(iface, accesspoint):
    information = {}
    command = "sudo iwlist " + iface + " scan | grep -E \"Cell|Quality|ESSID\""
    aps = return_command_output(command).decode("utf8")
    aps = aps.split("\n")

    cell_indices = list()
    for index in range(0, len(aps)):
        line_no_whitespace = ' '.join(aps[index].split())
        parts = line_no_whitespace.split()
        if parts[0] == "Cell":
            cell_indices.append(index)

    for index in cell_indices:
        line0 = ' '.join(aps[index].split())
        ap_mac = line0.split()[-1]
        ap_mac = ap_mac.replace(":", "-")
        information[ap_mac] = {}
        line1 = ' '.join(aps[index + 1].split())
        parts = line1.split()
        information[ap_mac]["drillTest"] = float(parts[2].split("=")[1])
        line2 = ' '.join(aps[index + 2].split())
        parts = line2.split(":")
        information[ap_mac][str(parts[1].replace('"', ''))] = information[ap_mac]["drillTest"]

    return information

def convert_info_to_json(accesspoint, essid, mac, bit_rate, tx_power, link_quality, signal_level, probe_no, information, location_name, test_device_location_description, nat_network):
    overall_dictionary = {}
    overall_dictionary["macAddress"] = "\"" + str(mac) + "\""
    overall_dictionary["accesspoint"] = "\"" + str(accesspoint) + "\""
    overall_dictionary["essid"] = "\"" + str(essid) + "\""
    bit_rate = int(float(bit_rate))
    overall_dictionary["bitRate"] = str(bit_rate)
    tx_power = int(float(tx_power))
    overall_dictionary["txPower"] = str(tx_power)
    link_quality = int(float(link_quality))
    overall_dictionary["linkQuality"] = str(link_quality)
    signal_level = int(float(signal_level))
    overall_dictionary["signalLevel"] = str(signal_level)
    overall_dictionary["probeNo"] = str(probe_no)
    information = json.dumps(information)
    overall_dictionary["monitor"] = information
    overall_dictionary["locationName"] = "\"" + str(location_name) + "\""
    overall_dictionary["testDeviceLocationDescription"] = "\"" + str(test_device_location_description) + "\""
    overall_dictionary["nat"] = "\"" + str(nat_network) + "\""
    json_data = json.dumps(overall_dictionary)
    return json_data

def stream_data(data):
    headers = {'content-type':"application/json"}
    try:
        session = requests.Session()
        session.verify = False
        session.post(url='https://WAS_FQDN:443/wifimon/probes/', data=data, headers=headers, timeout=30)
    except:
        pass

def set_location_information():
    location_name = ""
    test_device_location_description = ""
    nat_network = ""
    return location_name, test_device_location_description, nat_network

def wireless_info():
    location_name, test_device_location_description, nat_network = set_location_information()
    iface_name = find_wlan_iface_name()
    mac = get_mac(iface_name)
    bit_rate, tx_power, link_quality, signal_level, accesspoint, essid = parse_iwconfig(iface_name)
    information = parse_iwlist(iface_name, accesspoint)
    probe_no = ""
    json_data = convert_info_to_json(accesspoint, essid, mac, bit_rate, tx_power, link_quality, signal_level, probe_no, information, location_name, test_device_location_description, nat_network)
    stream_data(json_data)

if  == "":
    wireless_info()

The following values should be set:

  • "probe_no" (line 109) should match the number assigned to the testtools of the particular WiFiMon Hardware Probe (WHP), e.g. for the WHP assigned the number 1, the value should be "1". Assigning numbers to WHPs is possible by appropriately setting the testtool attribute included in the websites monitored by them. More information related to assigning number to WHPs is available in the WiFiMon Test Server installation guide.
  • "WAS_FQDN" (line 93) should match the FQDN of the WiFiMon Analysis Server (WAS) responsible for processing the wireless performance metrics of the WHP. The above code block assumes that the WAS uses https and port 443.
  • LInes 98 to 100 can be filled with more information regarding the location of the WHP.

That's all! At this point you may (optionally) unplug the keyboard, the mouse and the monitor and let the WHP measure the performance of your wireless network!

Security Issues

We suggest that you take additional efforts to safeguard the security of your probes:

  • Set the password for the "pi" user and the "root" user of the WiFiMon Hardware Probe.
  • Disable auto-login to the WiFiMon Hardware Probe. Open the terminal and type "sudo raspi-config". Then, from the third line "Boot Options", select "B1. Desktop / CLI" and then "B3. Desktop".
  • When connecting to your Wi-Fi network, your password will be stored as plaintext to the file "/etc/wpa_supplicant/wpa_supplicant.conf". Use the following commands to hash your ESSID and password:
set +o history
wpa_passphrase YOUR_ESSID YOUR_PASSWORD
set -o history

A "psk=....." line will be generated. Add this line in /etc/wpa_supplicant/wpa_supplicant.conf under your ESSID and delete the plaintext password.

  • Default user "pi" comes with sudo privileges. You can remove them with the following commands from the "root" user:
delgroup pi sudo
rm /etc/sudoers.d/010_pi-nopasswd
  • Convert the privileges of the "/etc/wpa_supplicant/wpa_supplicant.conf" to "600".
  • You may configure a firewall to further protect your device.


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