Network scanner on ESP8266

esp8266_scan.ino

/**
 * ESP8266 Scanner - Scans for networks on the 2.4GHz band and prints them out to the console.
 * Program it onto your ESP8266, pull up miniterm, the Serial Monitor, etc, and view a list of
 *  wireless networks on your computer.
 * Requres Arduino JSON (http://arduinojson.org/), downloadable from Library Manager or GitHub.
 * Or, set OUTPUT_JSON and consume the serial output with your favorite JSON parser.
 * 
 * Created by Leonora Tindall in 2017 for the ESP8266.
 * This software is licensed under the GNU General Public License, Version 3.0.
 */
#include <ESP8266WiFi.h>
#include <ArduinoJson.h>

// Uncomment to enable JSON format output
//#define OUTPUT_JSON
// Delay between scanning in milliseconds
#define SCAN_DELAY 1000
// The amount of memory to allocate for the static JSON buffer.
// Too large, and the stack will overflow into the heap.
// Too small, and the JSON construction will overflow its bounds.
// Turns out the ESP8266 just doesn't have that much RAM.
// 29000 bytes means about 21000 bytes left for stack.
#define JSON_BUFFER_SIZE 29000

StaticJsonBuffer<JSON_BUFFER_SIZE> jsonBuffer;

char* encTypeToString(int encType) {
  if (encType == ENC_TYPE_NONE) {
    return "none";
  }
  if (encType == ENC_TYPE_WEP) {
    return "wep";
  }
  if (encType == ENC_TYPE_TKIP) {
    return "wpa_psk";
  }
  if (encType == ENC_TYPE_CCMP) {
    return "wpa2_psk";
  }
  if (encType == ENC_TYPE_AUTO) {
    return "wpa_wpa2_psk";
  }
  return "wpa2_enterprise";
}

void printScanResultJSON(int networksFound) {
  JsonObject& root = jsonBuffer.createObject();
  JsonArray& ssidArray = root.createNestedArray("network_descriptions");
  root["networks"] = networksFound;
  for (int i = 0; i < networksFound; i++)
  {
    // To prevent watchdog killing us during printing
    delay(1);
    
    JsonObject& ssid = ssidArray.createNestedObject();
    ssid["essid"] = WiFi.SSID(i);
    ssid["bssid"] = WiFi.BSSIDstr(i);
    ssid["channel"] = WiFi.channel(i);
    ssid["rssi"] = WiFi.RSSI(i);
    ssid["security"] = encTypeToString(WiFi.encryptionType(i));
  }
  root.printTo(Serial);
}

void printScanResult(int networksFound)
{
  for (int i = 0; i < networksFound; i++)
  {
    // To prevent watchdog killing us during printing
    delay(1);
    Serial.printf("[ESP8266] %d: %s (%s), Ch:%d (%ddBm) %s\n", i + 1, WiFi.SSID(i).c_str(), WiFi.BSSIDstr(i).c_str(), WiFi.channel(i), WiFi.RSSI(i), encTypeToString(WiFi.encryptionType(i)));
  }
  Serial.println();
}

void setup() {
  // Initialize LED pin as an output, so it can be used to inform the user when scanning occurs.
  pinMode(LED_BUILTIN, OUTPUT);
  // Set up serial communication at 115200 baud.
  Serial.begin(115200);

  // Print banner to satisfy impatient users.
  #ifndef OUTPUT_JSON
  Serial.println("[ESP8266] ESP8266 Scanner starting up.");
  #endif
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  int nSsids = WiFi.scanNetworks(false, true);
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  #ifndef OUTPUT_JSON
  printScanResult(nSsids);
  #else
  printScanResultJSON(nSsids);
  #endif
  delay(SCAN_DELAY);                       // wait for a second
}