[ Day16] Esp32s用AP mode + Relay - (程序码讲解)

1.前言

今天依旧接续之前没讲完程序码，这次主要是讲loop里面的程序码，那此次主要介绍较为主要的部份，但由於这部分稍长，所以会挑一些讲，另外补充些额外的内容，剩下就会丢给後天那篇文章。

2.HTTP状态码

状态码是在说明当手机或各种装置(可上网页)，当连接至网页服务器时所回覆状态，包含连接正常，或服务器离线等等，我这样讲大家可能听不太懂，那我说个大家容易听见的404，许多人都会在连接网路时，如果连接不到或者网路不好时都会发生404 Not Found，那通常404 Not Found是服务器不想给使用者知道为何连线被拒绝，那下面就稍微介绍一些常见状态码。

2-1.状态码：2xx 连接成功

代表服务器接受使用者的请求，但通常各位看不见，因为接受就直接进网页拉，不会像常见的4xx状态码一样会显示在网页上。

2-2.状态码：4xx 客户端错误

这类的状态码代表了客户端看起来可能发生了错误，妨碍了服务器的处理。典型的就像403、404等等。

那这边就不多介绍拉，因为主要就是要说Esp32s开启网页时，也是会有状态码，那如果要看详细的可以到 HTTP状态码 wiki 查看。

3.程序码

void loop(){
  WiFiClient client = server.available();   // Listen for incoming clients

  if (client) {                             // If a new client connects,
    Serial.println("New Client.");          // print a message out in the serial port
    String currentLine = "";                // make a String to hold incoming data from the client
    while (client.connected()) {            // loop while the client's connected
      if (client.available()) {             // if there's bytes to read from the client,
        char c = client.read();             // read a byte, then
        Serial.write(c);                    // print it out the serial monitor
        header += c;
        if (c == '\n') {                    // if the byte is a newline character
          // if the current line is blank, you got two newline characters in a row.
          // that's the end of the client HTTP request, so send a response:
          if (currentLine.length() == 0) {
            // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
            // and a content-type so the client knows what's coming, then a blank line:
            client.println("HTTP/1.1 200 OK");
            client.println("Content-type:text/html");
            client.println("Connection: close");
            client.println();
            
            // turns the GPIOs on and off
            if (header.indexOf("GET /23/on") >= 0) {
              Serial.println("GPIO 23 on");
              output0State = "on";
              digitalWrite(output0, HIGH);
            } else if (header.indexOf("GET /23/off") >= 0) {
              Serial.println("GPIO 23 off");
              output0State = "off";
              digitalWrite(output0, LOW);
            } else if (header.indexOf("GET /22/on") >= 0) {
              Serial.println("GPIO 22 on");
              output2State = "on";
              digitalWrite(output2, HIGH);
            } else if (header.indexOf("GET /22/off") >= 0) {
              Serial.println("GPIO 22 off");
              output2State = "off";
              digitalWrite(output2, LOW);
            }
            
            // Display the HTML web page
            client.println("<!DOCTYPE html><html>");
            client.println("<head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">");
            client.println("<link rel=\"icon\" href=\"data:,\">");
            // CSS to style the on/off buttons 
            // Feel free to change the background-color and font-size attributes to fit your preferences
            client.println("<style>html { font-family: Helvetica; display: inline-block; margin: 0px auto; text-align: center;}");
            client.println(".button { background-color: #4CAF50; border: none; color: white; padding: 16px 40px;");
            client.println("text-decoration: none; font-size: 30px; margin: 2px; cursor: pointer;}");
            client.println(".button2 {background-color: #555555;}</style></head>");
            
            // Web Page Heading
            client.println("<body><h1>ESP32 Web Server</h1>");
            
            // Display current state, and ON/OFF buttons for GPIO 23  
            client.println("<p>GPIO 23 - State " + output0State + "</p>");
            // If the output0State is off, it displays the ON button       
            if (output0State=="off") {
              client.println("<p><a href=\"/23/on\"><button class=\"button\">ON</button></a></p>");
            } else {
              client.println("<p><a href=\"/23/off\"><button class=\"button button2\">OFF</button></a></p>");
            } 
               
            // Display current state, and ON/OFF buttons for GPIO 22  
            client.println("<p>GPIO 22 - State " + output2State + "</p>");
            // If the output2State is off, it displays the ON button       
            if (output2State=="off") {
              client.println("<p><a href=\"/22/on\"><button class=\"button\">ON</button></a></p>");
            } else {
              client.println("<p><a href=\"/22/off\"><button class=\"button button2\">OFF</button></a></p>");
            }
            client.println("</body></html>");
            
            // The HTTP response ends with another blank line
            client.println();
            // Break out of the while loop
            break;
          } else { // if you got a newline, then clear currentLine
            currentLine = "";
          }
        } else if (c != '\r') {  // if you got anything else but a carriage return character,
          currentLine += c;      // add it to the end of the currentLine
        }
      }
    }
    // Clear the header variable
    header = "";
    // Close the connection
    client.stop();
    Serial.println("Client disconnected.");
    Serial.println("");
  }
}

从程序码部分开始看，从43行开始会侦测是否有使用者连接，并抓取使用者资讯，而45行会判断是否有使用者连接，如果有则往46行走，没有结束(直接到loop结尾)