Receiving a HTTP POST Request on Arduino

Question

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

Answer 1

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 
#include 

// 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("");
    client.println(" ");
    // 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("
");
    }
    client.println("
");
    client.println("");
    client.println("");
    client.println("
");
    client.println(" ");
  }

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");
  }
}