// SPDX-License-Identifier: LGPL-3.0-or-later
// Copyright 2016-2025 Hristo Gochkov, Mathieu Carbou, Emil Muratov
//
// SSE example
//
#include <Arduino.h>
#include <AsyncTCP.h>
#include <WiFi.h>
#include <ESPAsyncWebServer.h>
static const char *htmlContent PROGMEM = R"(
<!DOCTYPE html>
<html>
<head>
<title>Server-Sent Events</title>
<script>
if (!!window.EventSource) {
var source = new EventSource('/events');
source.addEventListener('open', function(e) {
console.log("Events Connected");
}, false);
source.addEventListener('error', function(e) {
if (e.target.readyState != EventSource.OPEN) {
console.log("Events Disconnected");
}
}, false);
source.addEventListener('message', function(e) {
console.log("message", e.data);
}, false);
source.addEventListener('heartbeat', function(e) {
console.log("heartbeat", e.data);
}, false);
}
</script>
</head>
<body>
<h1>Open your browser console!</h1>
</body>
</html>
)";
static const size_t htmlContentLength = strlen_P(htmlContent);
static AsyncWebServer server(80);
static AsyncEventSource events("/events");
void setup() {
Serial.begin(115200);
#ifndef CONFIG_IDF_TARGET_ESP32H2
WiFi.mode(WIFI_AP);
WiFi.softAP("esp-captive");
#endif
// curl -v http://192.168.4.1/
server.on("/", HTTP_GET, [](AsyncWebServerRequest *request) {
// need to cast to uint8_t*
// if you do not, the const char* will be copied in a temporary String buffer
request->send(200, "text/html", (uint8_t *)htmlContent, htmlContentLength);
});
events.onConnect([](AsyncEventSourceClient *client) {
Serial.printf("SSE Client connected! ID: %" PRIu32 "\n", client->lastId());
client->send("hello!", NULL, millis(), 1000);
});
events.onDisconnect([](AsyncEventSourceClient *client) {
Serial.printf("SSE Client disconnected! ID: %" PRIu32 "\n", client->lastId());
});
server.addHandler(&events);
server.begin();
}
static uint32_t lastSSE = 0;
static uint32_t deltaSSE = 3000;
static uint32_t lastHeap = 0;
void loop() {
uint32_t now = millis();
if (now - lastSSE >= deltaSSE) {
events.send(String("ping-") + now, "heartbeat", now);
lastSSE = millis();
}
if (now - lastHeap >= 2000) {
Serial.printf("Free heap: %" PRIu32 "\n", ESP.getFreeHeap());
lastHeap = now;
}
}