New to Arduino - Need advice with a project...

Using Arduino Programming Questions
1

Hello,
First off I would like to say what a great little device the Arduino is.
I have recently purchased a SunFounder Mega 2560 R3 ATmega2560-16AU Board and a W5100 Ethernet Shield for a Project I am working on for my home automation system. Also I am some what new to coding so please bear with me. I have created a series of switch inputs for my hard wired door and window magnetic switches that are hooked to the Arduino. The programing for that was pretty straight forward so I won't go into that. Where I am having an issue is getting the Anduino to send a POST command to my main automation system via RESTful Web. A friend that is much better at coding than I suggested the following code as an example but I cant seem to get it work. In essence each switch state requires a discrete RESTful Web call to the automation systems API. For the moment I just need to figure out why the following code doesn't work, from there I should be able to figure the rest out.

#include <Ethernet.h>

byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
byte ip[] = { 192, 168, 0, 10 };                     
byte gateway[] = { 192, 168, 0, 1 };                 
byte subnet[] = { 255, 255, 255, 0 };
byte server[] = { 192, 168, 0, 100 };               

Client client(server, 8732);

void setup()
{
  Ethernet.begin(mac, ip, gateway, subnet);
  Serial.begin(9600);
  
  delay(1000);
  Serial.println("connecting...");
  
  if (client.connect()) {
    Serial.println("connected");
    client.println("POST http://xxx.xxx.xxx.xxx:8732/API/Sensor%201/ON HTTP/1.1");
    client.println("Content-type: application/x-www-form-urlencoded");
    client.println("Content-length: 28");                             
    client.println("Connection: Close");
    client.println();

  } else {
    Serial.println("connection failed");
  }
}
2 
    client.println("POST http://xxx.xxx.xxx.xxx:8732/API/Sensor%201/ON HTTP/1.1");

xxx.xxx.xxx.xxx ?

I have never seen an IP address like that before.

3

I should have known that was coming... :smiley:
The actual IP is 192.168.1.74

4

The request should be written as:

POST /API/Sensor%201/ON HTTP/1.1
Host: 192.168.0.10:8732
Connection: Close
Content-Type: application/x-www-form-urlencoded
Content-Length: 15

x=hello&y=world
5

There are three lines of code I don't understand. Could you please explain there function?

Content-Type: application/x-www-form-urlencoded
Content-Length: 15

x=hello&y=world
6

An HTTP POST request is made up from a set of request headers, and the request body.
Content-Type tells the server the format of the request body, application/x-www-form-urlencoded means the data is a set of name=value pairs serparated by '&' and is the format web browsers send when submitting html forms.
Content-Length tells the server how long the request body is.
The x=hello&y=world is the request body, here I just did an example for sending two parameters, one called x with the value "hello", the second called y with the value "world".

7

Have you tried making a similar request from your PC using Python or Ruby (for example). I suspect you would find it easier to get advice for that sort of project. Then if it works on your PC it should work with an Arduino.

...R

8

An HTTP POST request is made up from a set of request headers, and the request body.
Content-Type tells the server the format of the request body, application/x-www-form-urlencoded means the data is a set of name=value pairs serparated by '&' and is the format web browsers send when submitting html forms.
Content-Length tells the server how long the request body is.
The x=hello&y=world is the request body, here I just did an example for sending two parameters, one called x with the value "hello", the second called y with the value "world".