Can't commute a relay with Arduino wifi shield + Xively - arduino

Question

I’m trying to turn on and off an LED light bulb connected to a Tinterkit Relay.
I’m using an Arduino UNO r3 connected to internet thanks to an official Arduino Wifi shield.
I’ve done a simple website with two buttons to send a 1 (on) or a 0 (off) to my Xively account.
I’ve written a code to detect the last posted channel value. The code is working fine and I’m able to detect a 1 or a 0 every 3 seconds approximately. The problem is that the relay doesn’t commute.
Please please, I would appreciate a lot your help to solve this problem.
Here is the code:
#include <SPI.h>
#include <WiFi.h>
#include <HttpClient.h>
#include <Xively.h>
#include <TinkerKit.h>
char ssid[] = "XXXXXX";
char pass[] = "XXXXXX";
int state;
int status = WL_IDLE_STATUS;
char myIntStream[]="LED";
char xivelyKey[] = "XXXXXX";
#define FEED_ID XXXXXX
TKMosFet relay(O0);
XivelyDatastream datastreams[] = {
XivelyDatastream(myIntStream, strlen(myIntStream), DATASTREAM_INT),
};
XivelyFeed feed(FEED_ID,datastreams,1);
WiFiClient client;
XivelyClient xivelyclient(client);
void printWifiStatus() {
Serial.print("SSID: ");
Serial.println(WiFi.SSID());
IPAddress ip = WiFi.localIP();
Serial.print("IP Address: ");
Serial.println(ip);
long rssi = WiFi.RSSI();
Serial.print("signal strength (RSSI):");
Serial.print(rssi);
Serial.println(" dBm");
}
void setup() {
Serial.begin(9600);
Serial.println("LED light bulb");
Serial.println();
while ( status != WL_CONNECTED) {
Serial.println("Connecting to internet ...");
status = WiFi.begin(ssid, pass);
Serial.println("");
delay(5000);
}
Serial.println("Connected to wifi");
printWifiStatus();
}
void loop() {
Serial.println();
Serial.print("Datastream is:");
Serial.println(datastreams[0]);
Serial.print("LED value = ");
state = datastreams[0].getInt();
Serial.print(state);
if(state == 0){
relay.off();
Serial.println(" => Light is on.");
}
else if(state == 1){
relay.on();
Serial.println(" => Light is off.");
}
xivelyclient.get(feed, xivelyKey);
}