Esp32-cam, esp8266, WiFi, Bluetooth, MCU, hotspot create embedded DNS server

ESP32-CAM ArduinoIDE Development series article catalog

Chapter one ：ESP32-CAM High cost performance WIFI Quick start tutorial of image transmission scheme
Second articles ：ESP32-CAM The first wireless lighting program
Third articles ：ESP32-CAM Design and implementation of intelligent gateway
Fourth articles ：ESP32-CAM Create a hot spot composition and style DNS The server

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Preface

    daodanjishui The core original technology of the Internet of things ESP32 Arduino IDE Development of embedded web server setup 、http Request sending, receiving and parsing 、 Single chip microcomputer IO Oral reading and writing operation 、AJAX technology 、 Concurrent server technology and DNS Technology integration constitutes ：ESP32-CAM Create a hot spot composition and style DNS The server

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One 、ESP32-CAM Create a hot spot composition and style DNS What is the server ？

     The style of the code has changed （ I also used another foreigner's code for reference and tried it out new arduino library ESPAsyncWebServer）, The expansion degree becomes higher when the function remains roughly the same , Added two popular features ：
    （1） Constitute a parallel server , The servers in the first three articles can only respond to the requests of one client , All are modifications to the original official procedures , Now the server in Chapter 4 can receive requests from multiple clients at the same time , Concurrent response to client requests , Another unofficial program is used . This new library is very powerful , Support WebSocket function , I will use it later WebSocket Make a cluster control robot system .
    （2） LAN DNS Domain name resolution , That is to say ESP32-cam As a AP Hotspot sharing WIFI Resources and as an embedded server of the Internet of things , Even on WIFI Mobile devices in the browser input ：http://daodanjishui.com You can view the home page of the server , The first three phases of the design can only input the web address printed out by the module serial port assistant to connect to the server . In this issue, you only need to enter the domain name , After successfully opening the server home page, you can view the server's IP Address , Mom no longer has to worry that I have to use the serial port debugging assistant to connect to the server . If the students want to make a wireless remote control car without adding a display screen , I strongly recommend learning this code ！
    （3） Because I don't want to complicate things , There is no integrated video function and STA The function of mode , Because the video function involves image transmission , It is impossible to simply use
new arduino library ESPAsyncWebServer Complete the graphic design , The same goes for foreigners . Generally, this embedded server has a large amount of code , At least there are tens of thousands of lines ,
The following is the interface display , But I replaced all the server code , Because I have higher needs in the future ：

The following is the video address for the operation and debugging of the system ：https://v.youku.com/v_show/id_XNTE3OTAyNzUwNA==.html

Watch the video directly

ESP32-CAM Create a hot spot composition and style DNS The server

Two 、 The system design

1. Import and stock in

#include <AsyncTCP.h> and #include <ESPAsyncWebServer.h> and #include <FS.h> and #include <DNSServer.h>
After importing and warehousing, the server logic is designed , At first glance, the code is not complicated ：

void setup()
{
    
   Serial.begin(115200);
   // WiFi.mode(WIFI_AP_STA);// Set mode to AP+STA
    WiFi.mode(WIFI_AP); // Set to AP Pattern 
    WiFi.softAP("DNSServer");
    Serial.println("AP Setup completed ");
    IPAddress myIP = WiFi.softAPIP();
    Serial.print("AP IP address: ");
    Serial.println(myIP);
   dnsserver.start(DNS_PORT, "daodanjishui.com",myIP); // start-up DNS service ,daodanjishui Is the registered domain name 
   server.on("/", HTTP_GET, [](AsyncWebServerRequest *request){
    // Login home 
    request->send(200, "text/html", index_html(WiFi.softAPIP().toString()) );  
  });

Load a string after the server is started index_html As an embedded home page , Enter the server's IP The address can trigger the loading of the home page ：

String  index_html(String WiFiAddr){
return  String("")+"<html> <meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" /"+
"  <head>  "+
// Some of the JavaScript Code 
"  <body>  "+
"    <h1>daodanjishui ESP32 Lighting procedure </h1><p>     "+
"        <form action=\"\" method=\"\" name=\"\" >"+
"         Click on the trigger AjAX technology <br>   "+
"         <input type=\"text\" value=\"on\" name=\"inputcmd\" id=\"cmd\" size=\"10\" maxlength=\"20\" >                                   "+
"         <input type=\"button\" value=\"cmd\" οnclick=\"checkCmd(this.form.inputcmd.value)\" ><br>   "+
"        "+
"         <input type=\"text\" value=\"off\" name=\"inputcmd1\" id=\"cmd1\" size=\"10\" maxlength=\"20\" >                                   "+
"         <input type=\"button\" value=\"cmd\" οnclick=\"checkCmd(this.form.inputcmd1.value)\" ><br> "+
"               "+
"          Feedback :"+
"         <span id=\"result\"></span>  "+
"        </form> "+
"        "+
"        "+
"     <form action=\"control\" method=\"get\">"+
"   <table align=\"center\" width=\"450\">"+
"     <tr>"+
"       <td align=\"center\" colspan=\"2\">"+
"         <h2> Submit form instruction test </h2>"+
"         <hr>"+
"       </td>"+
"     </tr>"+
"     <tr>"+
"       <td align=\"right\"> Instructions ：</td>"+
"       <td><input type=\"text\" name=\"var\" value=\"on\" /></td>"+
"     </tr>"+
"     <tr>"+
"       <td align=\"right\"> The number ：</td>"+
"       <td><input type=\"text\" name=\"val\" value=\"168\"/></td>"+
"     </tr>"+
""+
"     <tr>"+
"       <td align=\"center\" colspan=\"2\">"+
"         <input type=\"submit\" value=\" send out \">"+
"         <a href=\"/control?var=on&val=888\"> Turn on the light quickly </a> "+
"          <a >ESP32 Server IP:"+ WiFiAddr+"</a> "+
"       </td>"+
"     </tr>"+
"   </table>"+
" </form>"+
"     "+
"  </body>"+
"</html>";
}

2. Read in the data submitted by the client

Read the... Submitted by the client get Request to judge whether the light is on or off .
The code is as follows （ Example ）：

 server.on("/control", HTTP_GET, [](AsyncWebServerRequest *request){
    // Respond to the logic of turning on the light 
    int paramsNr = request->params();
    Serial.println(paramsNr);
    for(int i=0;i<paramsNr;i++){
    
    AsyncWebParameter* p = request->getParam(i);
    Serial.print("Param name: ");
    Serial.println(p->name());
    Serial.print("Param value: ");
    Serial.println(p->value());
    Serial.println("------");
    int value_length=p->value().length();
    char value_buf[value_length];
    strcpy(value_buf,p->value().c_str());  
         if(!strcmp(value_buf, "on")){
    // If the received string is "on" 
          controlLamp(true);// turn on the light 
          return request->send(200, "text/plain", "on ok"); 
          }else if(!strcmp(value_buf, "off")){
         
          controlLamp(false);// Turn off the lights  
          return request->send(200, "text/plain", "off ok"); 
         }else if(!strcmp(value_buf, "check")){
    // Check the status of the lamp  
          int LAMP_flag= digitalRead(LAMP_PIN);// Read the status of the pin , And back to HIGH  or LOW 
           if(LAMP_flag==HIGH){
    
              return request->send(200, "text/plain", "LAMP is on");
           }else if(LAMP_flag==LOW){
    
             return request->send(200, "text/plain", "LAMP is off");
            }
         }
    }
    request->send(200, "text/plain", "message received");    
  });

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3、 ... and 、 Simulation and debugging

Load source code ：

Even on ESP32CAM Emitted AP hotspot

Mobile phone login ESP32CAM Home page

Mobile browser controls lighting

summary

     This paper mainly does the LAN domain name resolution （DNS）, Using library functions to achieve , Not much code , But the scalability is very high , If the reader has studied the code in Articles 3 and 4 , Then you can definitely learn two styles of coding , It's definitely worth it . With this function , Internet of things devices can achieve wireless control and access , And mine can also display servers ＩＰ Address . The code has been debugged for a long time , I have tried many schemes , Finally, a different scheme from the previous three projects was adopted , It can also be said to have grown out of nothing , The official source code has been changed beyond recognition , What comes out is the essence . In the next phase, add the wireless distribution network function of the server , Total use AP Pattern , No, STA Pattern , This ESP32-cam Still can't be in line with the world .ESP32 There are many ways to play after connecting to the Internet , such as MQTT Biography 、 mobile phone app Remote control 、 Voice Announcements 、VR Image transmission and somatosensory control , Coming soon .

Code and data download address ：https://www.cirmall.com/circuit/19386/
Point, I'll jump