Useful notebook to connect to WiFi

wifi_connect.ipynb

{
 "cells": [
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   "cell_type": "markdown",
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   "source": [
    "# Onboard WIFI\n",
    "\n",
    "Some boards can have embedded WIFI modules which allow users to connect\n",
    "to WIFI network. The same WIFI module can be used for:\n",
    "\n",
    "1. Serving as a wireless access point for users to access directly to the board.\n",
    "2. Connecting to an existing WIFI network.\n",
    "\n",
    "This notebook shows how to switch between the above two functions."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import os\n",
    "import subprocess\n",
    "from time import sleep\n",
    "import netifaces"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Configure interface\n",
    "The interface configuration has to be prepared in order to use \n",
    "`ifup` and `ifdown` commands."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "with open('/etc/network/interfaces.d/wlan0', 'w') as f:\n",
    "    f.write('auto wlan0\\n')\n",
    "    f.write('iface wlan0 inet manual\\n')\n",
    "    f.write('wpa-conf /etc/wpa_supplicant.conf')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Configure network\n",
    "The following cell allows users to choose their own WIFI network."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "_ = os.system(\"wpa_cli remove_network all\")\n",
    "_ = os.system(\"wpa_cli save_config\")\n",
    "\n",
    "with open('/etc/wpa_supplicant.conf', 'w') as f:\n",
    "    f.write(\"ctrl_interface=/var/run/wpa_supplicant\\n\")\n",
    "    f.write(\"update_config=1\\n\")\n",
    "\n",
    "ssid = input(\"WIFI network ID:\")\n",
    "passwd = input(\"WIFI password:\")\n",
    "_ = os.system(\"wpa_passphrase {0} {1} >> \"\n",
    "              \"/etc/wpa_supplicant.conf\".format(ssid, passwd))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Bring up `wlan0`\n",
    "By default, `wlan1` is used for wireless access point, `wlan0` is reserved\n",
    "for the use of WIFI connection to external network. The following cell\n",
    "will check whether `wlan0` is brought up properly."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "_ = os.system(\"wpa_cli -i wlan1 terminate\")\n",
    "_ = os.system(\"iw dev wlan1 del\")\n",
    "_ = os.system(\"ifup wlan0\")\n",
    "\n",
    "wlan0_found=False\n",
    "for i in range(5):\n",
    "    command = \"wpa_cli -i wlan0 ping\"\n",
    "    status = subprocess.run(\n",
    "             command.split(' '), \n",
    "             stdout=subprocess.PIPE).stdout.decode('utf-8').strip('\\n')\n",
    "    if status == \"PONG\":\n",
    "        wlan0_found=True\n",
    "        break\n",
    "    sleep(1)\n",
    "\n",
    "if wlan0_found:\n",
    "    print(\"Successfully found interface wlan0.\")\n",
    "else:\n",
    "    raise RuntimeError(\"Cannot find interface wlan0.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Connecting to WIFI\n",
    "With the configurations set above, we now try to connect to the WIFI network."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "wlan0 = netifaces.ifaddresses('wlan0')\n",
    "if netifaces.AF_INET6 not in wlan0:\n",
    "    _ = os.system(\"ifdown wlan0\")\n",
    "    _ = os.system(\"ifup wlan0\")\n",
    "\n",
    "_ = os.system(\"dhclient wlan0\")\n",
    "ip_found = False\n",
    "for index in range(10):\n",
    "    wlan0 = netifaces.ifaddresses('wlan0')\n",
    "    if netifaces.AF_INET not in wlan0:\n",
    "        sleep(3)\n",
    "    else:\n",
    "        ipv4 = netifaces.ifaddresses('wlan0')[netifaces.AF_INET][0]['addr']\n",
    "        ip_found = True\n",
    "        break\n",
    "\n",
    "if ip_found:\n",
    "    print(\"IPv4 address: {}\".format(ipv4))\n",
    "else:\n",
    "    raise RuntimeError(\"Cannot obtain IP address.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Change back to wireless access point\n",
    "After changing back, you will be able to use the WIFI access point again."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "_ = os.system(\"ifdown wlan0\")\n",
    "_ = os.remove('/etc/wpa_supplicant.conf')\n",
    "_ = os.remove('/etc/network/interfaces.d/wlan0')\n",
    "if os.system('systemctl restart wpa_ap'):\n",
    "    RuntimeError(\"Cannot restart wpa_ap service.\")"
   ]
  }
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