http request in time intervals

Question

I'm doing a program that receives data from a web page every so often, but only receives the data once and then receives everything blank. I need help to receive the data every time indefinitely. I am using arduino uno with arduino etherner shield

My code:

#include <SPI.h>
#include <Ethernet.h>
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 0, 177);
EthernetClient client;
int REDLed= 2;
int GREENLed= 3;
int BLUELed= 4;
void setup()
{ 
 pinMode(REDLed, OUTPUT);
 pinMode(GREENLed, OUTPUT);
 pinMode(GREENLed, OUTPUT);
 Ethernet.begin(mac, ip);
 Serial.begin(9600);
 Serial.println("power up" );
 delay(3000); 
}
void loop()
{
 Serial.println("SubmitHttpRequest - started" );
 SubmitHttpRequest();
 Serial.println("SubmitHttpRequest - finished" );
 delay(10000);
}
void SubmitHttpRequest()
{
 if (client.connect(server, 80))
 {
 Serial.println("connected");
 client.println("GET /arduino/getstate.php?color=All HTTP/1.1");
 client.println("Host: cybertodo.mx");
 client.println("Connection: close");
 client.println();
 }
 else
 {
 Serial.println("connection failed");
 }
 delay(100);
 changeLed();
}
void changeLed()
{
 String content = "";
 Serial.println(client.available());
 while(client.available()!=0)
 { 
 content = content + String(char (client.read()));
 }
 Serial.println(content);
 if(content.substring(30,31)== "1")
 {
 digitalWrite(REDLed, HIGH);
 }
 else if (content.substring(30,31)== "0")
 {
 digitalWrite(REDLed, LOW);
 }
 if(content.substring(31,32)== "1")
 {
 digitalWrite(GREENLed, HIGH);
 }
 else if (content.substring(31,32)== "0")
 {
 digitalWrite(GREENLed, LOW);
 }
 if(content.substring(32,33)== "1")
 {
 digitalWrite(BLUELed, HIGH);
 }
 else if (content.substring(32,33)== "0")
 {
 digitalWrite(BLUELed, LOW);
 }
 content = "";
}

• Dave X: Looks like you might be looping faster than the client.avaiable() is receiving data. Consider what happens if you only get half the response at a time -- the ifs drop though, you delete the content, then exit the changeLed() and de-allocate content. Consider making content global, and acting and clearing only when you get a full message.

Answer 1

Immediately after making the request when reading client.available() will be 0 since no data was received yet so:

 while(client.available()!=0)
 { 
 content = content + String(char (client.read()));
 }

Will never actually run. Try something like:

unsigned long last = millis();
String content = "";
while(client.connected()) {
 int len = client.available();
 if(len > 0) {
 last = millis();
 char buff[len];
 for(int i = 0; i < len; i++) {
 buff[i] = client.read();
 }
 content += String(buff);
 } else {
 if(millis() - last > 2000) {
 client.stop();
 return;
 }
 delay(1);
 }
}

Also note if you use Connection: close on the client then you must close the connection. This example doesn't do that until 2 seconds have passed. To do this properly you'd need to also add header parsing to your client and close the connection once the amount specified in Content-Length is received.