Another “Swiss Army Knife” for PLC Networks : Raspberry Pi 3


We can turn Raspberry pi 3 as  AP(Access point) and can be utilized with wireless devices to scan PLCs or field devices network.


1.Raspberry pi 3

2.Power Supply (for Raspberry)

3.Wireless device ( tablet, laptop, or cellphone)

4.Ethernet cable

Keep in the mind that the following procedure is for Raspberry Pi 3 (Jessie raspbian)  which I am quite sure it might work for some  older versions with slightly modifications. I got the script from several sources online and I did modification to work on  PLC network that use static IP addresses.

1.Install hostapd, udhcpd and iptables

Install the necessary tools
  1. sudo apt-get update
  2. sudo apt-get install hostapd udhcpd -y
  3. sudo apt-get install iptables -y


2. Create back up for these files, in case of installation failed.

  1. sudo touch /etc/network/interfaces.bak
  2. sudo cp /etc/network/interfaces /etc/network/interfaces.bak
  3. sudo touch /etc/dhcpcd.bak
  4. sudo cp /etc/dhcpcd.conf /etc/dhcpcd.bak


3.Build the following  script (

Basically this script is to create several configuration (conf) files and will load them into default ones. DHCP (Dynamic Host Configuration Protocol)  configuration will give away the dynamic  IP addresses between and to your wireless devices and to access wlan0  meanwhile it will give a static IP address for raspberry pi:  . For older version , it is necessary to setup configuration on /etc/network/interfaces for interfacing with network (wlan0,eth0, etc )  but on newest Jessie installation, the network configuration is located on /etc/dhcpcd.conf . HostAPD configuration will create hotspot and APN ( Access Point Name). The next is NAT (Network Address Translation ) which works as a translator between external router that connect to eth0 and WIFI guests who access  wlan0.    :

  1. #! /bin/bash
  2. #1. Configure DHCP----------------------------------------------
  3. x=tem.tem
  4. touch $x
  5. sudo rm -rf /etc/default/udhcpd
  6. #sudo mkdir /etc/default
  7. sudo touch /etc/default/udhcpd
  8. echo "start " >>   $x
  9. echo "end" >> $x
  10. echo "interface wlan0" >> $x
  11. echo "remaining yes" >> $x
  12. echo "opt dns" >> $x
  13. echo "opt subnet" >> $x
  14. echo "opt router" >> $x
  15. echo "opt lease 864000" >> $x
  16. sudo mv  $x /etc/udhcpd.conf
  17. touch $x
  18. echo  "# Comment the following line to enable" >> $x
  19. echo "#DHCPD_ENABLED=\"no\"" >> $x
  20. echo "# Options to pass to busybo>> $x
  21. echo "DHCPD_OPTS=\"-S\"" >> $x
  22. sudo mv $x  /etc/default/udhcpd
  23.         #give the Pi a static IP address
  24. sudo ifconfig wlan0
  25. #2.------------------------------SETUP AP (Access Point) Interface -------------------------------
  26. touch  $x
  27. echo "source-directory /etc/network/interfaces.d" >> $x
  28. echo "auto lo" >> $x
  29. echo "iface lo inet loopback" >> $x
  30. echo "" >> $x
  31. echo "auto eth0" >> $x
  32. echo "iface eth0 inet dhcp" >> $x
  33. echo "" >> $x
  34. echo "iface wlan0 inet static" >> $x
  35. echo "    address" >> $x
  36. echo "    netmask" >> $x
  37. echo "    wireless-power off" >> $x
  38. echo "" >> $x
  39. echo "iface default inet dhcp" >> $x
  40. echo "up iptables-restore < /etc/iptables.ipv4.nat" >> $x
  41. sudo chmod --reference=/etc/network/interfaces $x
  42. sudo chown --reference=/etc/network/interfaces $x
  43. sudo mv $x  /etc/network/interfaces.ap
  44. sudo chmod --reference /etc/network/interfaces.bk /etc/network/interfaces.ap
  45. #3. Configure HostAPD------------------------------------------------
  46. touch $x
  47. echo "interface=wlan0" >> $x
  48. echo "driver=nl80211" >> $x
  49. echo "ssid=WifiPLC" >> $x
  50. echo "hw_mode=g" >> $x
  51. echo "channel=6" >> $x
  52. echo "macaddr_acl=0" >> $x
  53. echo "auth_algs=1" >> $x
  54. echo "ignore_broadcast_ssid=0" >> $x
  55. echo  "wpa=0" >> $x
  56. echo "wpa_passphrase=My_Passphrase" >> $x
  57. echo "wpa_key_mgmt=WPA-PSK" >> $x
  58. echo "wpa_pairwise=TKIP" >> $x
  59. echo "rsn_pairwise=CCMP" >> $x
  60. echo "ieee80211n=1"   >> $x
  61. echo "wmm_enabled=1" >> $x
  62. echo "ht_capab=[HT40][SHORT-GI-20][DSSS_CCK_40]" >> $x
  63. sudo mv  $x  /etc/hostapd/hostapd.conf
  64. #4. Configure NAT--------------------------------------------
  65. touch $x
  66. echo "DAEMON_CONF=\"/etc/hostapd/hostapd.conf\"" >> $x
  67. sudo mv $x /etc/default/hostapd
  68. touch $x
  69. sudo sh -c "echo 1 >> /proc/sys/net/ipv4/ip_forward"
  70. sudo echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf
  71. sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
  72. sudo iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
  73. sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
  74. sudo sh -c "iptables-save >> /etc/iptables.ipv4.nat"
  75. #------------------------------5. Fire it up! R----------------------------------------
  76. sudo service hostapd start
  77. sudo service udhcpd start
  78. #-----------------------------6.get the hotspot to start on boot----------------------
  79. sudo update-rc.d hostapd enable
  80. sudo update-rc.d udhcpd enable
  81. #------------------------Create
  82. sudo apt-get install dnsmasq -y
  83. sudo service dnsmasq start
  84. sudo update-rc.d dnsmasq enable
  85. sudo apt-get install udhcpc -y


4.Create script
  1. sudo nano script
  1. #! /bin/bash
  2. #sudo cp  /etc/init.d/hostapd.bak /etc/init.d/hostapd
  3. #sudo cp /etc/init.d/udhcpd.bak /etc/init.d/udhcpd
  4. sudo /etc/init.d/hostapd stop
  5. sudo /etc/init.d/udhcpd stop
  6. sudo ifdown wlan0
  7. sudo ifconfig wlan0 down
  8. sudo rm -rf /etc/network/interfaces
  9. sudo cp /etc/network/interfaces.ap /etc/network/interfaces
  10. sudo ifconfig wlan0 up
  11. sudo ifup wlan0
  12. sudo service hostapd start
  13. sudo service udhcpd start
  14. sudo service hostapd status


Run and

run wifi and AP
  1. sudo ./
  2. sudo ./


If there is no errors , you should able to see SSID name “WifiPLC” on your wireless devices under WIFI setting menu. Login and when ask the password, type “My_Passphrase”  that will save and connect it to your wireless devices. To test it, connect eth0 (ethernet port) on Raspberry Pi  to DHCP router that connect to Internet. The router will assign a dynamic IP address . Now you are able to connect to Internet. Type “” on your phone browser to verify it.

This is last step if you need a static IP  and skip it if  you just need dynamic IP address . Eth0  still has a dynamic IP address and will not communicate with PLC static IP address network. Identify gateway address and check all existing PLC IP address and find a static IP address for Raspberry PI that will not cause conflicts with other numbers. In this example the gateway is and the number has not been used by other PLCs is To activate a static IP address, add the following to the very bottom of /etc/dhcpcd.conf file.

  1. # static IP setup
  2. interface eth0
  3. static ip_address=
  4. static routers=
  5. static domain_name_servers=


Save it as  /etc/dhcpcd.conf.

Reboot your Raspberry Pi , connect Ethernet port to  a PLC  router. Now if you have PLC CPUs  or Ethernet  modules  which have  “192.168.1.xx ” , type those number on your browser. Let says “”. Most new Field devices or PLCs  have HTTP protocol capability on port 80/8080, so you will  see something like this  :


Using Raspbian shell terminal, we can find MAC number using “arp’ command,  install “nmap” utility to explore and troubleshoot  the network such as scanning particular IP address blocks, checking open/closed ports etc.

Press Ctrl+C to copy the following code.