Espressif Systems ESP8266 Beginner's Manual page 29

Serial.println(WiFi.localIP()); // Send the IP address of the ESP8266 to the computer
if (MDNS.begin("esp8266")) { // Start the mDNS responder for esp8266.local
Serial.println("mDNS responder started");
} else {
Serial.println("Error setting up MDNS responder!");
}
server.on("/", HTTP_GET, handleRoot); // Call the 'handleRoot' function when a client requests URI "/"
server.on("/login", HTTP_POST, handleLogin); // Call the 'handleLogin' function when a POST request is made to URI "/login"
server.onNotFound(handleNotFound); // When a client requests an unknown URI (i.e. something other than "/"), call function
"handleNotFound"
server.begin(); // Actually start the server
Serial.println("HTTP server started");
}
void loop(void){
server.handleClient(); // Listen for HTTP requests from clients
}
void handleRoot() { // When URI / is requested, send a web page with a button to toggle the LED
server.send(200, "text/html", "<form action=\"/login\" method=\"POST\"><input type=\"text\" name=\"username\"
placeholder=\"Username\"></br><input type=\"password\" name=\"password\" placeholder=\"Password\"></br><input type=\"submit\"
value=\"Login\"></form><p>Try 'John Doe' and 'password123' ...</p>");
}
void handleLogin() { // If a POST request is made to URI /login
if( ! server.hasArg("username") || ! server.hasArg("password")
|| server.arg("username") == NULL || server.arg("password") == NULL) { // If the POST request doesn't have username and password
data
server.send(400, "text/plain", "400: Invalid Request"); // The request is invalid, so send HTTP status 400
return;
}
if(server.arg("username") == "John Doe" && server.arg("password") == "password123") { // If both the username and the password are
correct
server.send(200, "text/html", "<h1>Welcome, " + server.arg("username") + "!</h1><p>Login successful</p>");
} else { // Username and password don't match
server.send(401, "text/plain", "401: Unauthorized");
}
}
void handleNotFound(){
server.send(404, "text/plain", "404: Not found"); // Send HTTP status 404 (Not Found) when there's no handler for the URI in the
request
}
The HTML in handleRoot is:
<form action="/login" method="POST">
<input type="text" name="username" placeholder="Username"></br>
<input type="password" name="password" placeholder="Password"></br>
<input type="submit" value="Login">
</form>
<p>
Try 'John Doe' and 'password123' ...
</p>
Upload the sketch and go to http://esp8266.local/, then type 'John Doe' into the username field, and 'password123' into the password
field, and click 'Login'. You should get a welcome screen. If you leave on or both of the fields blank, you should get a 400 (Bad
Request) error. If you enter a wrong username or password, you should get a 401 (Unauthorized) error.
The data of the POST body can be accessed using
. The key name on the ESP8266 corresponds to the name argument in the HTML form on the web page.
server.hasArg("key")
When we get a POST request, we first check if the necessary arguments (username and password) are present. If that's not the case,
we send a 400 (Invalid Request) status.
Then we check if the credentials match 'John Doe' & 'password123'. If that's the case, we respond with a status 200 (Ok) and a
welcome page. If the username and/or password doesn't match, we send a 401 (Unauthorized) status.
Inline functions
In the previous examples, we passed
cases however, it's more readable to just write the definition of the function inline, like so:
void setup(){
// ...
server.onNotFound([](){
server.send(404, "text/plain", "404: Not found");
});
}
server.arg("key")
and to the
handleRoot handleNotFound
, and you can check if a specific key exists using
function as a parameter (callback function). In some
server.on