DNSServer refactoring, switch to AsyncUDP (#7482)

* DNSServer: switch to AsyncUDP instead of WiFiUDP AsyncUDP offers event driven approch for handling udp dns req's WiFiUDP hooks to loop() for packet processing and making useless malloc's each run * DNSServer code refactoring get rid of intermediate mem buffers and extra data copies, most of the data could be referenced or copied from the source packet - removed _buffer member - replaced DNSQuestion.QName from uint8_t[] to char* added sanity checks for mem bounds optimize label/packet length calculations other code cleanup * DNSServer drop dynamically allocated member structs DNSHeader and DNSQuestion structs could be created on stack no need to keep it as obj members * DNSServer: labels min length checks, simplified labels parser * DNSServer use default settings for catch-all setup - default constructor and start() method simply runs a catch-all DNS setup - avoid string comparison for domain reqs in catch-all mode - use IPaddress class for _resolvedIP (looking for IPv6 support in future) * CaptivePortal example refactored - use webserver instead of simple tcp setver - use redirects to allows CaptivePortal detection pop-ups in modern systems * DNSServer status getters added add isUp() method - returns 'true' if server is up and UDP socket is listening for UDP req's add isCaptive() method - returns 'true' if server runs in catch-all (captive portal mode) some doxygen comments added start() method now keeps existing IP address if any --------- Co-authored-by: Lucas Saavedra Vaz <[email protected]> Co-authored-by: Me No Dev <[email protected]>
espressif · Dec 18, 2023 · d912710 · d912710
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diff --git a/libraries/DNSServer/examples/CaptivePortal/CaptivePortal.ino b/libraries/DNSServer/examples/CaptivePortal/CaptivePortal.ino
@@ -1,52 +1,59 @@
+/*
+This example enables catch-all Captive portal for ESP32 Access-Point
+It will allow modern devices/OSes to detect that WiFi connection is
+limited and offer a user to access a banner web-page.
+There is no need to find and open device's IP address/URL, i.e. http://192.168.4.1/
+This works for Android, Ubuntu, FireFox, Windows, maybe others...
+*/
+
+#include <Arduino.h>
 #include <WiFi.h>
 #include <DNSServer.h>
+#include <WebServer.h>
+
 
-const byte DNS_PORT = 53;
-IPAddress apIP(8,8,4,4); // The default android DNS
 DNSServer dnsServer;
-WiFiServer server(80);
+WebServer server(80);
+
+static const char responsePortal[] = R"===(
+<!DOCTYPE html><html><head><title>ESP32 CaptivePortal</title></head><body>
+<h1>Hello World!</h1><p>This is a captive portal example page. All unknown http requests will 
+be redirected here.</p></body></html>
+)===";
+
+// index page handler
+void handleRoot() {
+  server.send(200, "text/plain", "Hello from esp32!");
+}
 
-String responseHTML = ""
-  "<!DOCTYPE html><html><head><title>CaptivePortal</title></head><body>"
-  "<h1>Hello World!</h1><p>This is a captive portal example. All requests will "
-  "be redirected here.</p></body></html>";
+// this will redirect unknown http req's to our captive portal page
+// based on this redirect various systems could detect that WiFi AP has a captive portal page
+void handleNotFound() {
+  server.sendHeader("Location", "/portal");
+  server.send(302, "text/plain", "redirect to captive portal");
+}
 
-void setup() { 
+void setup() {
+  Serial.begin(115200);
   WiFi.mode(WIFI_AP);
   WiFi.softAP("ESP32-DNSServer");
-  WiFi.softAPConfig(apIP, apIP, IPAddress(255, 255, 255, 0));
 
-  // if DNSServer is started with "*" for domain name, it will reply with
-  // provided IP to all DNS request
-  dnsServer.start(DNS_PORT, "*", apIP);
+  // by default DNSServer is started serving any "*" domain name. It will reply
+  // AccessPoint's IP to all DNS request (this is requred for Captive Portal detection)
+  dnsServer.start();
+
+  // serve a simple root page
+  server.on("/", handleRoot);
+
+  // serve portal page
+  server.on("/portal",[](){server.send(200, "text/html", responsePortal);});
 
+  // all unknown pages are redirected to captive portal
+  server.onNotFound(handleNotFound);
   server.begin();
 }
 
 void loop() {
-  dnsServer.processNextRequest();
-  WiFiClient client = server.available();   // listen for incoming clients
-
-  if (client) {
-    String currentLine = "";
-    while (client.connected()) {
-      if (client.available()) {
-        char c = client.read();
-        if (c == '\n') {
-          if (currentLine.length() == 0) {
-            client.println("HTTP/1.1 200 OK");
-            client.println("Content-type:text/html");
-            client.println();
-            client.print(responseHTML);
-            break;
-          } else {
-            currentLine = "";
-          }
-        } else if (c != '\r') {
-          currentLine += c;
-        }
-      }
-    }
-    client.stop();
-  }
+  server.handleClient();
+  delay(5);   // give CPU some idle time
 }