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ESP8266WiFi Scan Class

ESP8266WiFi Library 🔙

Scan Class

This class is represented in Arduino WiFi library by scanNetworks() function. Developers of esp8266 / Arduino core extend this functionality by additional methods and properties.

Table of Contents

Documentation of this class is divided into two parts. First covers functions to scan for available networks. Second describes what information is collected during scanning process and how to access it.

Scan for Networks

Scanning for networks takes hundreds of milliseconds to complete. This may be done in a single run when we are triggering scan process, waiting for completion, and providing result - all by a single function. Another option is to split this into steps, each done by a separate function. This way we can execute other tasks while scanning is in progress. This is called asynchronous scanning. Both methods of scanning are documented below.

scanNetworks

Scan for available Wi-Fi networks in one run and return the number of networks that has been discovered.

WiFi.scanNetworks()

There is on overload of this function that accepts two optional parameters to provide extended functionality of asynchronous scanning as well as looking for hidden networks.

WiFi.scanNetworks(async, show_hidden)

Both function parameters are of boolean type. They provide the flowing functionality:

  • asysnc - if set to true then scanning will start in background and function will exit without waiting for result. To check for result use separate function scanComplete that is described below.
  • show_hidden - set it to true to include in scan result networks with hidden SSID.

scanComplete

Check for result of asynchronous scanning.

WiFi.scanComplete()

On scan completion function returns the number of discovered networks.

If scan is not done, then returned value is < 0 as follows:

  • Scanning still in progress: -1
  • Scanning has not been triggered: -2

scanDelete

Delete the last scan result from memory.

WiFi.scanDelete()

scanNetworksAsync

Start scanning for available Wi-Fi networks. On completion execute another function.

WiFi.scanNetworksAsync(onComplete, show_hidden)

Function parameters:

  • onComplete - the event handler executed when the scan is done
  • show_hidden - optional boolean parameter, set it to true to scan for hidden networks

Example code:

#include "ESP8266WiFi.h"

void prinScanResult(int networksFound)
{
  Serial.printf("%d network(s) found\n", networksFound);
  for (int i = 0; i < networksFound; i++)
  {
    Serial.printf("%d: %s, Ch:%d (%ddBm) %s\n", i + 1, WiFi.SSID(i).c_str(), WiFi.channel(i), WiFi.RSSI(i), WiFi.encryptionType(i) == ENC_TYPE_NONE ? "open" : "");
  }
}


void setup()
{
  Serial.begin(115200);
  Serial.println();

  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
  delay(100);

  WiFi.scanNetworksAsync(prinScanResult);
}


void loop() {}

Example output:

5 network(s) found
1: Tech_D005107, Ch:6 (-72dBm)
2: HP-Print-A2-Photosmart 7520, Ch:6 (-79dBm)
3: ESP_0B09E3, Ch:9 (-89dBm) open
4: Hack-4-fun-net, Ch:9 (-91dBm)
5: UPC Wi-Free, Ch:11 (-79dBm)

Show Results

Functions below provide access to result of scanning. It does not matter if scanning has been done in synchronous or asynchronous mode, scan results are available using the same API.

Individual results are accessible by providing a `networkItem' that identifies the index (zero based) of discovered network.

SSID

Return the SSID of a network discovered during the scan.

WiFi.SSID(networkItem)

Returned SSID is of the String type. The networkItem is a zero based index of network discovered during scan.

encryptionType

Return the encryption type of a network discovered during the scan.

WiFi.encryptionType(networkItem)

Function returns a number that encodes encryption type as follows:

  • 5 : ENC_TYPE_WEP - WEP
  • 2 : ENC_TYPE_TKIP - WPA / PSK
  • 4 : ENC_TYPE_CCMP - WPA2 / PSK
  • 7 : ENC_TYPE_NONE - open network
  • 8 : ENC_TYPE_AUTO - WPA / WPA2 / PSK

The networkItem is a zero based index of network discovered during scan.

RSSI

Return the RSSI (Received Signal Strength Indication) of a network discovered during the scan.

WiFi.RSSI(networkItem)

Returned RSSI is of the int32_t type. The networkItem is a zero based index of network discovered during scan.

BSSID

Return the BSSID (Basic Service Set Identification) that is another name of MAC address of a network discovered during the scan.

WiFi.BSSID(networkItem)

Function returns a pointer to the memory location (an uint8_t array with the size of 6 elements) where the BSSID is saved.

If you do not like to pointers, then there is another version of this function that returns a String.

WiFi.BSSIDstr(networkItem)

The networkItem is a zero based index of network discovered during scan.

channel

Return the channel of a network discovered during the scan.

WiFi.channel(networkItem)

Returned channel is of the int32_t type. The networkItem is a zero based index of network discovered during scan.

isHidden

Return information if a network discovered during the scan is hidden or not.

WiFi.isHidden(networkItem)

Returned value if the bolean type, and true means that network is hidden. The networkItem is a zero based index of network discovered during scan.

getNetworkInfo

Return all the network information discussed in this chapter above in a single function call.

WiFi.getNetworkInfo(networkItem, &ssid, &encryptionType, &RSSI, *&BSSID, &channel, &isHidden)

The networkItem is a zero based index of network discovered during scan. All other input parameters are passed to function by reference. Therefore they will be updated with actual values retrieved for particular networkItem. The function itself returns boolean true or false to confirm if information retrieval was successful or not.

Example code:

int n = WiFi.scanNetworks(false, true);

String ssid;
uint8_t encryptionType;
int32_t RSSI;
uint8_t* BSSID;
int32_t channel;
bool isHidden;

for (int i = 0; i < n; i++)
{
  WiFi.getNetworkInfo(i, ssid, encryptionType, RSSI, BSSID, channel, isHidden);
  Serial.printf("%d: %s, Ch:%d (%ddBm) %s %s\n", i + 1, ssid.c_str(), channel, RSSI, encryptionType == ENC_TYPE_NONE ? "open" : "", isHidden ? "hidden" : "");
}

Example output:

6 network(s) found
1: Tech_D005107, Ch:6 (-72dBm)
2: HP-Print-A2-Photosmart 7520, Ch:6 (-79dBm)
3: ESP_0B09E3, Ch:9 (-89dBm) open
4: Hack-4-fun-net, Ch:9 (-91dBm)
5: , Ch:11 (-77dBm)  hidden
6: UPC Wi-Free, Ch:11 (-79dBm)

For code samples please refer to separate section with examples ➡️ dedicated specifically to the Scan Class.