Receiving a HTTP POST Request on Arduino

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悲哀的现实
悲哀的现实 2021-01-31 12:41

Is it possible to receive a HTTP Post request with my Arduino Uno using a Ethernet shield. I want to make an Android app wich can control me Arduino and I thought the best way t

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  • 2021-01-31 13:21

    A POST looks like:

    POST /test.php HTTP/1.1
    Host: 192.168.0.55
    Content-Type: application/x-www-form-urlencoded
    Connection: close
    User-Agent: Arduino/1.0
    Content-Length: 1024
    
    data=5
    

    So you have to ignore first "newline" and read on. Here is my modified Web Server code to read posted data:

    /*
      Web Server 
    */
    
    #include <SPI.h>
    #include <Ethernet.h>
    
    // Enter a MAC address and IP address for your controller below.
    // The IP address will be dependent on your local network:
    byte mac[] = {
      0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
    };
    IPAddress ip(192, 168, 15, 177);
    
    // Initialize the Ethernet server library
    // with the IP address and port you want to use
    // (port 80 is default for HTTP):
    EthernetServer server(80);
    
    void setup() {
      // Open serial communications and wait for port to open:
      Serial.begin(9600);
      while (!Serial) {
        ; // wait for serial port to connect. Needed for native USB port only
      }
    
    
      // start the Ethernet connection and the server:
      //Ethernet.begin(mac, ip);
      Ethernet.begin(mac);
      server.begin();
      Serial.print("server is at ");
      Serial.println(Ethernet.localIP());
    }
    
    
      void writeResponse(EthernetClient client) {
        // send a standard http response header
        client.println("HTTP/1.1 200 OK");
        client.println("Content-Type: text/html");
        client.println("Connection: close");  // the connection will be closed after completion of the response
        // client.println("Refresh: 5");  // refresh the page automatically every 5 sec
    
        client.println();
        client.println("<!DOCTYPE HTML>");
        client.println("<html> <body>");
        // output the value of each analog input pin
        for (int analogChannel = 0; analogChannel < 6; analogChannel++) {
          int sensorReading = analogRead(analogChannel);
          client.print("analog input ");
          client.print(analogChannel);
          client.print(" is ");
          client.print(sensorReading);
          client.println("<br />");
        }
        client.println("<form action=\"\" method=\"post\">");
        client.println("<input type=\"submit\" value=\"On\" name=\"btnOn\">");
        client.println("<input type=\"submit\" value=\"Off\" name=\"btnOff\">");
        client.println("</form>");
        client.println("</body> </html>");
      }
    
    void loop() {
      // listen for incoming clients
      EthernetClient client = server.available();
      if (client) {
        Serial.print("new client [");
        //Serial.print(client.getRemoteIP());
        //Serial.println("]");
    
        // an http request ends with a blank line
        boolean currentLineIsBlank = true;
        String req_str = "";
        int data_length = -1;
        boolean skip = true;
    
        //int empty_line_count = 0;
        while (client.connected()) 
        {
          if (client.available()) {
            char c = client.read();
            //Serial.write(c);
            req_str += c;
    
            // if you've gotten to the end of the line (received a newline
            // character) and the line is blank, the http request has ended,
            // so you can send a reply       
            if (c == '\n' && currentLineIsBlank && req_str.startsWith("GET")) {
              writeResponse(client);
              break;
            }
            if (c == '\n' && currentLineIsBlank && req_str.startsWith("POST") && !skip) {
              writeResponse(client);
              break;
            }   
            if (c == '\n' && currentLineIsBlank && req_str.startsWith("POST") && skip) {
              skip = false;
              String temp = req_str.substring(req_str.indexOf("Content-Length:") + 15);
              temp.trim();
              //Serial.print("Content-Length=");
              data_length = temp.toInt();
              /*Serial.println(data_length);
              writeResponse(client);
              break;*/
              while(data_length-- > 0)
              {
                c = client.read();
                req_str += c;
              }
              writeResponse(client);
              break;
            }
    
            if (c == '\n') {
              // you're starting a new line
              currentLineIsBlank = true;
            } else if (c != '\r') {
              // you've gotten a character on the current line
              currentLineIsBlank = false;
            }
          }
        }
    
        Serial.println(req_str);
    
        // give the web browser time to receive the data
        delay(1);
        // close the connection:
        client.stop();
        Serial.println("client disconnected");
      }
    }
    
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  • 2021-01-31 13:27

    I wanted to read a POST like you instead of using a GET. I did it like this:

    /*
     A simple Arduino Ethernet web server. 
     by John Harrison
     */
    
    #include <SPI.h>
    #include <Ethernet.h>
    
    // You can change the MAC and IP addresses to suit your network:
    
    byte mac[] = { 0X52, 0X64, 0X75, 0X69, 0X6E, 0X6F };
    IPAddress ip( 192,168,0,97 );
    
    EthernetServer server(80); // Port 80 is HTTP port
    char new_state[1024];
    
    void setup()
    {
      Serial.begin(9600);
      // Start the Ethernet server:
      Ethernet.begin(mac, ip);
    
      server.begin();
    
      // Set the digital pins ready to write to
      for (int pin = 2; pin <= 9; pin++) {
        pinMode(pin, OUTPUT);
      }
    
      Serial.print("Serving on http://");
      Serial.println(Ethernet.localIP());
    }
    
    void loop()
    {
      // listen for incoming clients
      EthernetClient client = server.available();
    
      if (client) {
    
        // Serial.println("Client connected");
    
        while (client.connected()) {
    
          int i = 0;
          int head = 1;
          int body = 0;
    
          while(client.available()) {
            char c = client.read();
            if (c == '\n') {
    
              if ( i <= 2 ) {
    
                // an http request ends with a blank line
    
                sendPage(client);
                if ( head == 1 ) {
                  body = 1;
                  head = 0;
                }
    
              }
    
              i = -1;
    
            }
            if ( body == 1 ) {
              new_state[i] = c;
            }
            i++;
            new_state[i] = '\0';
          }
          i = 0;
        }
    
        // Serial.println("Disconnected");
        /*
        if ( strlen(new_state) > 0 ){
          Serial.print ("[");
          Serial.print(new_state);
          Serial.println ("]");
        }
        */
        // Post data looks like pinD2=On
        if ( strncmp( new_state, "pinD", 4) == 0 ) {
          int pin = new_state[4] - 48; // Convert ascii to int
          // Serial.println(pin);
          if ( strncmp( new_state+5, "=On", 3) == 0 ) {
            digitalWrite(pin, 1);
          } 
          else if ( strncmp( new_state+5, "=Off", 4) == 0 ) {
            digitalWrite(pin, 0);
          }
        }
    
      }
    
    }
    
    void sendPage(EthernetClient client)
    {
    
      // Serial.println("Sending response");
    
      // send a standard http response header
      client.println("HTTP/1.0 200 OK\Content-Type: text/html\n\n<html>\n<head>");
      client.println("<link rel='icon' href='data:;base64,iVBORw0KGgo='>");
      client.println("<title>POST Pin controller</title>\n</head>\n<body>\n");
      client.println("<h2>Buttons turn pins on or off</h2>");
      client.println("<form method='post' action='/' name='pins'>");
    
      char line[1024];
      int pin;
    
      for ( pin=2; pin<=9; pin++ ) {
        sprintf(line, "<input name='pinD%d' type='submit' value='On' />\n", pin);
        client.print(line);
        sprintf(line, "<input name='pinD%d' type='submit' value='Off' /> %d<br />\n", pin, pin);
        client.print(line);
      }
    
      client.println("</form>\n</body>\n</html>");
      client.stop();
    
    }
    

    There are ways to do it which are simpler and smaller, but I found them quite laggy so have been trying to get it as fast as possible.

    I have used this to control 8 LEDs on pins 2-9 on a Mega 2560. I haven't tested it on a Uno yet, but I expect it would work the same.

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  • 2021-01-31 13:27

    Not sure about POST, but GET definitely works. Here's an AJAX example that I've been using that works. It just controls an RGB LED.

     xmlhttp.open("GET", "http://ipAddressOfArduino?r=" + redVal + "&g=" + greenVal + "&b=" + blueVal + "&e", true);
    

    Then on the Arduino side, I just parse the data.

    //ARDUINO 1.0+ ONLY
    //ARDUINO 1.0+ ONLY
    
    
    #include <Ethernet.h>
    #include <SPI.h>
    boolean reading = false;
    String myStr;
    int redVal, greenVal, blueVal;
    
    ////////////////////////////////////////////////////////////////////////
    //CONFIGURE
    ////////////////////////////////////////////////////////////////////////
      //byte ip[] = { 192, 168, 0, 1 };   //Manual setup only
      //byte gateway[] = { 192, 168, 0, 1 }; //Manual setup only
      //byte subnet[] = { 255, 255, 255, 0 }; //Manual setup only
    
      // if need to change the MAC address (Very Rare)
      byte mac[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
    
      EthernetServer server = EthernetServer(80); //port 80
    ////////////////////////////////////////////////////////////////////////
    
    void setup(){
      Serial.begin(9600);
    
      pinMode(3, OUTPUT);
      pinMode(5, OUTPUT);
      pinMode(6, OUTPUT);
    
      Ethernet.begin(mac);
      //Ethernet.begin(mac, ip); //for manual setup
    
      server.begin();
      Serial.println(Ethernet.localIP());
    
    }
    
    void loop(){
    
      // listen for incoming clients, and process qequest.
      checkForClient();
    
    }
    
    void checkForClient(){
    
      EthernetClient client = server.available();
    
      if (client) {
    
        // an http request ends with a blank line
        boolean currentLineIsBlank = true;
        boolean sentHeader = false;
        myStr = "";
        while (client.connected()) {
          if (client.available()) {
    
            char c = client.read();
    
            if(reading && c == ' ') reading = false;
            if(c == '?') reading = true; //found the ?, begin reading the info
    
            if(reading){
              //Serial.print(c);
              if (c!='?') {
                myStr += c;
              }
    
            }
    
            if (c == '\n' && currentLineIsBlank)  break;
    
            if (c == '\n') {
              currentLineIsBlank = true;
            }else if (c != '\r') {
              currentLineIsBlank = false;
            }
          }
        }
    
        parseThangs(myStr);
        analogWrite(3, redVal);
        analogWrite(5, greenVal);
        analogWrite(6, blueVal);    
        delay(100); // give the web browser time to receive the data
        client.stop(); // close the connection:    
      } 
    }
    
    void parseThangs(String str) {
      int startIndex = str.indexOf("r");
      int endIndex = str.indexOf("g");
      String redStr = str.substring(startIndex + 2, endIndex - 1);
      char tempRed[4];
      redStr.toCharArray(tempRed, sizeof(tempRed));
      redVal = atoi(tempRed);
      startIndex = str.indexOf("g");
      endIndex = str.indexOf("b");
      String greenStr = str.substring(startIndex + 2, endIndex -1);
      char tempGreen[4];
      greenStr.toCharArray(tempGreen, sizeof(tempGreen));
      greenVal = atoi(tempGreen);
      startIndex = str.indexOf("b");
      endIndex = str.indexOf("e");
      String blueStr = str.substring(startIndex + 2, endIndex -1);
      char tempBlue[4];
      blueStr.toCharArray(tempBlue, sizeof(tempBlue));
      blueVal = atoi(tempBlue);
      Serial.println(redStr + " " + greenStr + " " + blueStr);
    }
    

    Probably a little sloppy, but it works.

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