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I am trying to put a web server on my Wemos D1 mini pro. I am using this example for the Arduino code: https://github.com/wemos/Arduino_D1/blob/master/doc/esp8266wifi/server-examples.rst

#include <ESP8266WiFi.h>

const char* ssid = "GL-AR300M-ceb";
const char* password = "********";

WiFiServer server(80);

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

  Serial.printf("Connecting to %s ", ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(500);
    Serial.print(".");
  }
  Serial.println(" connected");

  server.begin();
  Serial.printf("Web server started, open %s in a web browser\n", WiFi.localIP().toString().c_str());
}


// prepare a web page to be send to a client (web browser)
String prepareHtmlPage()
{
  String htmlPage =
     String("HTTP/1.1 200 OK\r\n") +
            "Content-Type: text/html\r\n" +
            "Connection: close\r\n" +  // the connection will be closed after completion of the response
            "Refresh: 5\r\n" +  // refresh the page automatically every 5 sec
            "\r\n" +
            "<!DOCTYPE HTML>" +
            "<html>" +
            "Analog input:  " + String(analogRead(A0)) +
            "</html>" +
            "\r\n";
  return htmlPage;
}


void loop()
{
  WiFiClient client = server.available();
  // wait for a client (web browser) to connect
  if (client)
  {
    Serial.println("\n[Client connected]");
    while (client.connected())
    {
      // read line by line what the client (web browser) is requesting
      if (client.available())
      {
        String line = client.readStringUntil('\r');
        Serial.print(line);
        // wait for end of client's request, that is marked with an empty line
        if (line.length() == 1 && line[0] == '\n')
        {
          client.println(prepareHtmlPage());
          break;
        }
      }
    }
    delay(1); // give the web browser time to receive the data

    // close the connection:
    client.stop();
    Serial.println("[Client disonnected]");
  }
}

It uploads fine and when I open the serial monitor get this:

Connecting to GL-AR300M-ceb . connected Web server started, open 192.168.8.119 in a web browser

When I go to the IP address that it gives in the monitor, I only see a blank page. I also can't inspect element, so it doesn't load the HTML part I guess.
When I change the code like this: 

if (client.available())  
{  
//        String line = client.readStringUntil('\r');  
//        Serial.print(line);  
//        // wait for end of client's request, that is marked with an empty line  
//        if (line.length() == 1 && line[0] == '\n')  
//        {  
//          client.println(prepareHtmlPage());  
//          break;  
//        }  
          client.println(prepareHtmlPage());  
      }

then i see this
screenshot of code as plain text in browser

And when i add the break in the code like so: 

client.println(prepareHtmlPage());  
break;

in the code, i get the blank page again.

Does someone have an idea what the problem might be?

|improve this question
  • 2
    Why not use the far simpler ESP8266WebServer examples that come with the core? – Majenko♦ May 30 '18 at 9:43
  • Oh, thank you. Honestly, I didn't know about them yet! Let me try the HelloServer. – E. Bodt May 30 '18 at 9:56
  • 1
    It's a far simpler interface than trying to implement HTTP from the ground up. – Majenko♦ May 30 '18 at 9:56
  • Yes! I got it to work! Thank you for this tip! – E. Bodt Jun 1 '18 at 14:00
  • I'm no master. I don't believe there is ever a carriage return while requesting a web page. – Vick79 Nov 1 '18 at 1:58
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you should go for the "Advanced Webserver" example provided by the ESP8266 libraries in your Arduino IDE. The webserver is using callbacks like

server.on ( "/", handleRoot );
server.on ( "/test.svg", drawGraph );

and so on. Then you can use these handles to give back a html page to your browser like

server.send(200, "text/plain", message);       //Response to the HTTP request

Note how the function returns an 200 http code to your browser, which is mandatory for showing up your web page!

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