Ein WLAN-Netzfinder mit einem ESP8266.

//------------------------------------------------------------------------------------------------------------
 // WiFi Netzwerk-Scanner Demoprogramm mit ESP8266 ESP-01
 //------------------------------------------------------------------------------------------------------------
 //(c) Roland Elmiger, HB9GAA
 //
 // Version   1.0B
 //
 // Enwickelt am   : 26.05.2015
 // Letzter Update : 14.09.2015 A. Bieri http://www.esp8266.com/viewtopic.php?f=29&t=4612
 //------------------------------------------------------------------------------------------------------------

#include "ESP8266WiFi.h"

const char* WiFiSSID = "xxxxxx";
 const char* WiFiPSK = "password";
 // Host
 const char* host = "www.example.com";
 const int httpPort = 80;

// Initialisierung ...
 //------------------------------------------------------------------------------------------------------------
 void setup()
 {
 uart_div_modify(0, UART_CLK_FREQ / 115200); //damit Serial.printf verwendet werden kann
 Serial.begin(115200);

WiFi.mode(WIFI_STA);                        //WiFi als Station definieren
 WiFi.disconnect();                          //und eine ev. bestehende Verbindung trennen
 delay(100);
 Serial.printf("Initialisierung beendet\r\n");
 connectWiFi();
 Serial.printf("Verbindung aufgebaut\r\n");
 connectTCP();
 Serial.println("Stream geschlossen");
 }

//------------------------------------------------------------------------------------------------------------
 void connectWiFi()
 {
 // WiFI.begin([ssid], [passkey]) initiates a WiFI connection
 // to the stated [ssid], using the [passkey] as a WPA, WPA2,
 // or WEP passphrase.
 WiFi.begin(WiFiSSID, WiFiPSK);

// Use the WiFi.status() function to check if the ESP8266
 // is connected to a WiFi network.
 Serial.println("Im Netz registrieren");
 while (WiFi.status() != WL_CONNECTED)
 {
 delay(500);
 Serial.print(".");
 }
 Serial.println("");
 Serial.println("WiFi verbunden");
 Serial.println("IP Addresse: ");
 Serial.println(WiFi.localIP());
 }

//------------------------------------------------------------------------------------------------------------
 void connectTCP()
 {
 // connect to a web server and read stream
 // first open connection
 Serial.print("Connecting to ");
 Serial.println(host);

// Use WiFiClient class to create TCP connections
 WiFiClient client;
 if (!client.connect(host, httpPort)) {
 Serial.println("connection failed");
 return;
 }

// This will send the request to the server
 client.print(String("GET /") + " HTTP/1.1\r\n" + "Host: " + host + "\r\n" + "Connection: close\r\n\r\n");
 delay(10);

Serial.print("client.status(): ");
 Serial.println(client.status());
 Serial.print("client.available(): ");
 Serial.println(client.available());
 Serial.print("client.connected(): ");
 Serial.println(client.connected());

// Read all the lines of the reply from server and print them to Serial
 while(client.connected()){
 String line = client.readStringUntil('\r');
 Serial.print(line);
 }

delay(5000);
 }
 // Hauptprogramm ...
 //------------------------------------------------------------------------------------------------------------
 void loop()
 {
 Serial.printf("\r\nScan starten ...   ");
 int n = WiFi.scanNetworks();                //WiFi.scanNetworks gibt die Anzahl gefundene AP zurück
 Serial.printf("Scan beendet\n\n");

if (n == 0)
 Serial.printf("keine Netzwerke gefunden\r\n");
 else
 {
 Serial.printf("%2u Netzwerke gefunden  (* = ungesichertes Netzwerk)\n---------------------------------------------------\n", n);

for (int i = 0; i < n; ++i)        //SSID und RSSI fuer jedes gefundene Netzwerk ausgeben
 {
 Serial.printf("%2u: %s\t(%i dBm)%s ", i+1, (char*)WiFi.SSID(i), (char*)WiFi.RSSI(i));  printEncryptionType(WiFi.encryptionType(i));
 }
 }
 delay(5000);                         // etwas warten bis zum naechsten Scann
 }

// Verschlüsselungstyp ausgeben
 //------------------------------------------------------------------------------------------------------------
 void printEncryptionType(int thisType)
 {
 switch (thisType)
 {
 case ENC_TYPE_WEP:
 Serial.printf("WEP\n");
 break;

case ENC_TYPE_TKIP:
 Serial.printf("WPA\n");
 break;

case ENC_TYPE_CCMP:
 Serial.printf("WPA2\n");
 break;

case ENC_TYPE_NONE:
 Serial.printf("*\n");
 break;

case ENC_TYPE_AUTO:
 Serial.printf("Auto\n");
 break;
 }
 }