Arduino connection with the server failed

Question

I am trying to connect arduino uno and ethernet shield and try to send some data to an asp.net web api application. When i upload the sketch, i get in the serial monitor connection failed. I don't understand what's going wrong ? Below is the code i am using

#include "cactus_io_DHT22.h"
#include <SPI.h>
#include <Ethernet.h>
#include <Client.h>
#define DHT22_PIN 2
byte mac[] = {
 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xDD };
IPAddress ip(192,168,0,177);
IPAddress server(192,168,0,11);
EthernetClient client;
DHT22 dht(DHT22_PIN);
float heatindex1 =0.00;
float heatindex2 = 0.00;
void setup() {
 Ethernet.begin(mac,ip); 
 delay(1000); Serial.begin(9600); 
 Serial.println("connecting..."); 
 if (client.connect(server, 80)) {
 Serial.println("connected :D "); 
 }
 Serial.print("Arduino server IP address: ");
 Serial.println(Ethernet.localIP());
 Serial.println("DHT22 Humidity - Temperature Sensor");
 Serial.println("RH\t\tTemp (C)\tTemp (F)\tHeat Index (C)\t Heat Index 
 (F)\t Max(C)\t\t Min(C)");
 dht.begin();
 dht.readHumidity();
 dht.readTemperature();
}
float max1=dht.temperature_C;
 float min1=100;
void loop() {
 dht.readHumidity();
 dht.readTemperature();
 heatindex1=dht.computeHeatIndex_C();
 heatindex2=dht.computeHeatIndex_F();
 if(dht.temperature_C>max1)
 {max1=dht.temperature_C;}
 if(dht.temperature_C<min1)
 {min1=dht.temperature_C;}
 // Check if any reads failed and exit early (to try again).
 if (isnan(dht.humidity) || isnan(dht.temperature_C)) {
 Serial.println("DHT sensor read failure!");
 return;
 }
 if (client) {
 // When a client sends a request to a webserver, that request ends with a blank line
 boolean currentLineIsBlank = true;
 Serial.println("OK"); }
 if (client.connect(server, 80)) {
 client.print("GET /api/todo?humidity="); 
 client.print(dht.humidity);
 client.print("&temperature1="); 
 client.print(dht.temperature_C);
 client.print("&temperature2="); 
 client.print(dht.temperature_F);
 client.print("&heatindex1="); 
 client.print(heatindex1);
 client.print("&heatindex2="); 
 client.print(heatindex2);
 client.print("&max1="); 
 client.print(max1);
 client.print("&min1="); 
 client.print(min1);// And this is what we did in the testing section above. We are making a GET request just like we would from our browser but now with live data from the sensor
 client.println(" HTTP/1.1"); // Part of the GET request
 client.println("Host: 192.168.0.11"); // IMPORTANT: If you are using XAMPP you will have to find out the IP address of your computer and put it here (it is explained in previous article). If you have a web page, enter its address (ie.Host: "www.yourwebpage.com")
 client.println("Connection: close"); // Part of the GET request telling the server that we are over transmitting the message
 client.println(); // Empty line
 client.println(); // Empty line
 client.stop(); // Closing connection to server
 }
 else {
 //If Arduino can't connect to the server (your computer or web page)
 Serial.println("--> connection failed\n");
 }
 Serial.print(dht.humidity); Serial.print(" %\t\t");
 Serial.print(dht.temperature_C); Serial.print(" *C\t");
 Serial.print(dht.temperature_F); Serial.print(" *F\t");
 Serial.print(dht.computeHeatIndex_C()); Serial.print(" *C\t ");
 Serial.print(dht.computeHeatIndex_F()); Serial.print(" *F\t ");
 Serial.print(max1); Serial.print(" *C\t ");
 Serial.print(min1); Serial.println(" *C\t");
 delay(5000);
}

Answer 1

I don't know of this library, but you're using the connection code twice, once in the setup() and later again in the loop().

You're already checking whether the client exists:

if (client) {

Why are you asking a few lines down again to connect?

if (client.connect(server, 80)) {

My guess is, that this if()-Clause is not necessary. Or the connection in the setup() should be removed.

If this isn't the source of the error, first test whether the server on 192.168.0.11 is running and that you can connect (from a different device) to the port 80.