esp8266/doc/esp8266wifi/station-class.rst

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Station Class

The number of features provided by ESP8266 in the station mode is far more extensive than covered in original Arduino WiFi library. Therefore, instead of supplementing original documentation, we have decided to write a new one from scratch.

Description of station class has been broken down into four parts. First discusses methods to establish connection to an access point. Second provides methods to manage connection like e.g. reconnect or isConnected. Third covers properties to obtain information about connection like MAC or IP address. Finally the fourth section provides alternate methods to connect like e.g. Wi-Fi Protected Setup (WPS).

Table of Contents

• Start Here
  • begin
  • config
• Manage Connection
  • reconnect
  • disconnect
  • isConnected
  • setAutoConnect
  • getAutoConnect
  • setAutoReconnect
  • waitForConnectResult
• Configuration
  • macAddress
  • localIP
  • subnetMask
  • gatewayIP
  • dnsIP
  • hostname
  • status
  • SSID
  • psk
  • BSSID
  • RSSI
• Connect Different
  • WPS
  • Smart Config

Points below provide description and code snippets how to use particular methods.

For more code samples please refer to separate section with examples dedicated specifically to the Station Class.

Start Here

Switching the module to Station mode is done with begin function. Typical parameters passed to begin include SSID and password, so module can connect to specific Access Point.

WiFi.begin(ssid, password)

By default, ESP will attempt to reconnect to Wi-Fi network whenever it is disconnected. There is no need to handle this by separate code. A good way to simulate disconnection would be to reset the access point. ESP will report disconnection, and then try to reconnect automatically.

begin

There are several versions (called function overloads in C++) of begin function. One was presented just above: WiFi.begin(ssid, password). Overloads provide flexibility in number or type of accepted parameters.

The simplest overload of begin is as follows:

WiFi.begin()

Calling it will enable station mode and connect to the last used access point based on configuration saved in flash memory.

Notes:

• It is possible that calling begin will result in the module being in STA + softAP mode if the module was previously placed into AP mode.
• If you notice strange behavior with DNS or other network functionality, check which mode your module is in (see WiFi.mode() in the Generic Class Documentation).

Below is the syntax of another overload of begin with the all possible parameters:

WiFi.begin(ssid, password, channel, bssid, connect)

Meaning of parameters is as follows:

• ssid - a character string containing the SSID of Access Point we would like to connect to, may have up to 32 characters
• password to the access point, a character string that should be minimum 8 characters long and not longer than 64 characters
• channel of AP, if we like to operate using specific channel, otherwise this parameter may be omitted
• bssid - mac address of AP, this parameter is also optional
• connect - a boolean parameter that if set to false, will instruct module just to save the other parameters without actually establishing connection to the access point

config

Disable DHCP client (Dynamic Host Configuration Protocol) and set the IP configuration of station interface to user defined arbitrary values. The interface will be a static IP configuration instead of values provided by DHCP.

WiFi.config(local_ip, gateway, subnet, dns1, dns2)

Function will return true if configuration change is applied successfully. If configuration can not be applied, because e.g. module is not in station or station + soft access point mode, then false will be returned.

The following IP configuration may be provided:

• local_ip - enter here IP address you would like to assign the ESP station's interface
• gateway - should contain IP address of gateway (a router) to access external networks
• subnet - this is a mask that defines the range of IP addresses of the local network
• dns1, dns2 - optional parameters that define IP addresses of Domain Name Servers (DNS) that maintain a directory of domain names (like e.g. www.google.co.uk) and translate them for us to IP addresses

Example code:

#include <ESP8266WiFi.h>

const char* ssid = "********";
const char* password = "********";

IPAddress staticIP(192,168,1,22);
IPAddress gateway(192,168,1,9);
IPAddress subnet(255,255,255,0);

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

  Serial.printf("Connecting to %s\n", ssid);
  WiFi.config(staticIP, gateway, subnet);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected, IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {}

Example output:

Connecting to sensor-net
.
Connected, IP address: 192.168.1.22

Please note that station with static IP configuration usually connects to the network faster. In the above example it took about 500ms (one dot . displayed). This is because obtaining of IP configuration by DHCP client takes time and in this case this step is skipped. If you pass all three parameter as 0.0.0.0 (local_ip, gateway and subnet), it will re enable DHCP. You need to re-connect the device to get new IPs.

Manage Connection

reconnect

Reconnect the station. This is done by disconnecting from the access point an then initiating connection back to the same AP.

WiFi.reconnect()

Notes: 1. Station should be already connected to an access point. If this is not the case, then function will return false not performing any action. 2. If true is returned it means that connection sequence has been successfully started. User should still check for connection status, waiting until WL_CONNECTED is reported:

WiFi.reconnect();
while (WiFi.status() != WL_CONNECTED)
{
  delay(500);
  Serial.print(".");
}

disconnect

Sets currently configured SSID and password to null values and disconnects the station from an access point.

WiFi.disconnect(wifioff)

The wifioff is an optional boolean parameter. If set to true, then the station mode will be turned off.

isConnected

Returns true if Station is connected to an access point or false if not.

WiFi.isConnected()

setAutoConnect

Configure module to automatically connect on power on to the last used access point.

WiFi.setAutoConnect(autoConnect)

The autoConnect is an optional parameter. If set to false then auto connection functionality up will be disabled. If omitted or set to true, then auto connection will be enabled.

getAutoConnect

This is "companion" function to setAutoConnect(). It returns true if module is configured to automatically connect to last used access point on power on.

WiFi.getAutoConnect()

If auto connection functionality is disabled, then function returns false.

setAutoReconnect

Set whether module will attempt to reconnect to an access point in case it is disconnected.

WiFi.setAutoReconnect(autoReconnect)

If parameter autoReconnect is set to true, then module will try to reestablish lost connection to the AP. If set to false then module will stay disconnected.

Note: running setAutoReconnect(true) when module is already disconnected will not make it reconnect to the access point. Instead reconnect() should be used.

waitForConnectResult

Wait until module connects to the access point. This function is intended for module configured in station or station + soft access point mode.

WiFi.waitForConnectResult()

Function returns one of the following connection statuses:

• WL_CONNECTED after successful connection is established
• WL_NO_SSID_AVAIL in case configured SSID cannot be reached
• WL_CONNECT_FAILED if password is incorrect
• WL_IDLE_STATUS when Wi-Fi is in process of changing between statuses
• WL_DISCONNECTED if module is not configured in station mode
• -1 on timeout

Configuration

macAddress

Get the MAC address of the ESP station's interface.

WiFi.macAddress(mac)

Function should be provided with mac that is a pointer to memory location (an uint8_t array the size of 6 elements) to save the mac address. The same pointer value is returned by the function itself.

Example code:

if (WiFi.status() == WL_CONNECTED)
{
  uint8_t macAddr[6];
  WiFi.macAddress(macAddr);
  Serial.printf("Connected, mac address: %02x:%02x:%02x:%02x:%02x:%02x\n", macAddr[0], macAddr[1], macAddr[2], macAddr[3], macAddr[4], macAddr[5]);
}

Example output:

Mac address: 5C:CF:7F:08:11:17

If you do not feel comfortable with pointers, then there is optional version of this function available. Instead of the pointer, it returns a formatted String that contains the same mac address.

WiFi.macAddress()

Example code:

if (WiFi.status() == WL_CONNECTED)
{
  Serial.printf("Connected, mac address: %s\n", WiFi.macAddress().c_str());
}

localIP

Function used to obtain IP address of ESP station's interface.

WiFi.localIP()

The type of returned value is IPAddress. There is a couple of methods available to display this type of data. They are presented in examples below that cover description of subnetMask, gatewayIP and dnsIP that return the IPAdress as well.

Example code:

if (WiFi.status() == WL_CONNECTED)
{
  Serial.print("Connected, IP address: ");
  Serial.println(WiFi.localIP());
}

Example output:

Connected, IP address: 192.168.1.10

subnetMask

Get the subnet mask of the station's interface.

WiFi.subnetMask()

Module should be connected to the access point to obtain the subnet mask.

Example code:

Serial.print("Subnet mask: ");
Serial.println(WiFi.subnetMask());

Example output:

Subnet mask: 255.255.255.0

gatewayIP

Get the IP address of the gateway.

WiFi.gatewayIP()

Example code:

Serial.printf("Gataway IP: %s\n", WiFi.gatewayIP().toString().c_str());

Example output:

Gataway IP: 192.168.1.9

dnsIP

Get the IP addresses of Domain Name Servers (DNS).

WiFi.dnsIP(dns_no)

With the input parameter dns_no we can specify which Domain Name Server's IP we need. This parameter is zero based and allowed values are none, 0 or 1. If no parameter is provided, then IP of DNS #1 is returned.

Example code:

Serial.print("DNS #1, #2 IP: ");
WiFi.dnsIP().printTo(Serial);
Serial.print(", ");
WiFi.dnsIP(1).printTo(Serial);
Serial.println();

Example output:

DNS #1, #2 IP: 62.179.1.60, 62.179.1.61

hostname

Get the DHCP hostname assigned to ESP station.

WiFi.hostname()

Function returns String type. Default hostname is in format ESP_24xMACwhere 24xMAC are the last 24 bits of module's MAC address.

The hostname may be changed using the following function:

WiFi.hostname(aHostname)

Input parameter aHostname may be a type of char*, const char* or String. Maximum length of assigned hostname is 32 characters. Function returns either true or false depending on result. For instance, if the limit of 32 characters is exceeded, function will return false without assigning the new hostname.

Example code:

Serial.printf("Default hostname: %s\n", WiFi.hostname().c_str());
WiFi.hostname("Station_Tester_02");
Serial.printf("New hostname: %s\n", WiFi.hostname().c_str());

Example output:

Default hostname: ESP_081117
New hostname: Station_Tester_02

status

Return the status of Wi-Fi connection.

WiFi.status()

Function returns one of the following connection statuses:

• WL_CONNECTED after successful connection is established
• WL_NO_SSID_AVAIL in case configured SSID cannot be reached
• WL_CONNECT_FAILED if password is incorrect
• WL_IDLE_STATUS when Wi-Fi is in process of changing between statuses
• WL_DISCONNECTED if module is not configured in station mode

Returned value is type of wl_status_t defined in wl_definitions.h

Example code:

#include <ESP8266WiFi.h>

void setup(void)
{
  Serial.begin(115200);
  Serial.printf("Connection status: %d\n", WiFi.status());
  Serial.printf("Connecting to %s\n", ssid);
  WiFi.begin(ssid, password);
  Serial.printf("Connection status: %d\n", WiFi.status());
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.printf("\nConnection status: %d\n", WiFi.status());
  Serial.print("Connected, IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {}

Example output:

Connection status: 6
Connecting to sensor-net
Connection status: 6
......
Connection status: 3
Connected, IP address: 192.168.1.10

Particular connection statuses 6 and 3 may be looked up in wl_definitions.h as follows:

3 - WL_CONNECTED
6 - WL_DISCONNECTED

Basing on this example, when running above code, module is initially disconnected from the network and returns connection status 6 - WL_DISCONNECTED. It is also disconnected immediately after running WiFi.begin(ssid, password). Then after about 3 seconds (basing on number of dots displayed every 500ms), it finally gets connected returning status 3 - WL_CONNECTED.

SSID

Return the name of Wi-Fi network, formally called Service Set Identification (SSID).

WiFi.SSID()

Returned value is of the String type.

Example code:

Serial.printf("SSID: %s\n", WiFi.SSID().c_str());

Example output:

SSID: sensor-net

psk

Return current pre shared key (password) associated with the Wi-Fi network.

WiFi.psk()

Function returns value of the String type.

BSSID

Return the mac address of the access point to which the ESP module was directed to connect to. This address is formally called Basic Service Set Identification (BSSID). The returned pointer is what the user configured when calling begin() with a bssid argument. It does not_ necessarily reflect the mac address of the access point to which the ESP module's station interface is currently connected to.

WiFi.BSSID()

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

Below is similar function, but returning BSSID but as a String type.

WiFi.BSSIDstr()

Example code:

Serial.printf("BSSID: %s\n", WiFi.BSSIDstr().c_str());

Example output:

BSSID: 00:1A:70:DE:C1:68

RSSI

Return the signal strength of Wi-Fi network, that is formally called Received Signal Strength Indication (RSSI).

WiFi.RSSI()

Signal strength value is provided in dBm. The type of returned value is int32_t.

Example code:

Serial.printf("RSSI: %d dBm\n", WiFi.RSSI());

Example output:

RSSI: -68 dBm

Connect Different

ESP8266 SDK provides alternate methods to connect ESP station to an access point. Out of them esp8266 / Arduino core implements WPS and Smart Config as described in more details below.

WPS

The following beginWPSConfig function allows connecting to a network using Wi-Fi Protected Setup (WPS). Currently only push-button configuration (WPS_TYPE_PBC mode) is supported (SDK 1.5.4).

WiFi.beginWPSConfig()

Depending on connection result function returns either true or false (boolean type).

Example code:

#include <ESP8266WiFi.h>

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

  Serial.printf("Wi-Fi mode set to WIFI_STA %s\n", WiFi.mode(WIFI_STA) ? "" : "Failed!");
  Serial.print("Begin WPS (press WPS button on your router) ... ");
  Serial.println(WiFi.beginWPSConfig() ? "Success" : "Failed");

  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected, IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {}

Example output:

Wi-Fi mode set to WIFI_STA
Begin WPS (press WPS button on your router) ... Success
.........
Connected, IP address: 192.168.1.102

Smart Config

The Smart Config connection of an ESP module an access point is done by sniffing for special packets that contain SSID and password of desired AP. To do so the mobile device or computer should have functionality of broadcasting of encoded SSID and password.

The following three functions are provided to implement Smart Config.

Start smart configuration mode by sniffing for special packets that contain SSID and password of desired Access Point. Depending on result either true or `false is returned.

beginSmartConfig()

Query Smart Config status, to decide when stop configuration. Function returns either true or false ofboolean` type.

smartConfigDone()

Stop smart config, free the buffer taken by beginSmartConfig(). Depending on result function return either true or false of boolean type.

stopSmartConfig()

For additional details regarding Smart Config please refer to ESP8266 API User Guide.