Arduino wifi shield interfacing

/*
  Web client

 This sketch connects to a website (http://www.google.com)
 using a WiFi shield.

 This example is written for a network using WPA encryption. For
 WEP or WPA, change the WiFi.begin() call accordingly.

 This example is written for a network using WPA encryption. For
 WEP or WPA, change the WiFi.begin() call accordingly.

 Circuit:
 * WiFi shield attached

 created 13 July 2010
 by dlf (Metodo2 srl)
 modified 31 May 2012
 by Tom Igoe
 */


#include <SPI.h>
#include <WiFi101.h>
#include "arduino_secrets.h" 
///////please enter your sensitive data in the Secret tab/arduino_secrets.h
char ssid[] = SECRET_SSID;        // your network SSID (name)
char pass[] = SECRET_PASS;    // your network password (use for WPA, or use as key for WEP)
int keyIndex = 0;            // your network key Index number (needed only for WEP)

int status = WL_IDLE_STATUS;
// if you don't want to use DNS (and reduce your sketch size)
// use the numeric IP instead of the name for the server:
//IPAddress server(74,125,232,128);  // numeric IP for Google (no DNS)
char server[] = "www.google.com";    // name address for Google (using DNS)

// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
WiFiClient client;

void setup() {
  //Initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // check for the presence of the shield:
  if (WiFi.status() == WL_NO_SHIELD) {
    Serial.println("WiFi shield not present");
    // don't continue:
    while (true);
  }

  // attempt to connect to WiFi network:
  while (status != WL_CONNECTED) {
    Serial.print("Attempting to connect to SSID: ");
    Serial.println(ssid);
    // Connect to WPA/WPA2 network. Change this line if using open or WEP network:
    status = WiFi.begin(ssid, pass);

    // wait 10 seconds for connection:
    delay(10000);
  }
  Serial.println("Connected to wifi");
  printWiFiStatus();

  Serial.println("\nStarting connection to server...");
  // if you get a connection, report back via serial:
  if (client.connect(server, 80)) {
    Serial.println("connected to server");
    // Make a HTTP request:
    client.println("GET /search?q=arduino HTTP/1.1");
    client.println("Host: www.google.com");
    client.println("Connection: close");
    client.println();
  }
}

void loop() {
  // if there are incoming bytes available
  // from the server, read them and print them:
  while (client.available()) {
    char c = client.read();
    Serial.write(c);
  }

  // if the server's disconnected, stop the client:
  if (!client.connected()) {
    Serial.println();
    Serial.println("disconnecting from server.");
    client.stop();

    // do nothing forevermore:
    while (true);
  }
}


void printWiFiStatus() {
  // print the SSID of the network you're attached to:
  Serial.print("SSID: ");
  Serial.println(WiFi.SSID());

  // print your WiFi shield's IP address:
  IPAddress ip = WiFi.localIP();
  Serial.print("IP Address: ");
  Serial.println(ip);

  // print the received signal strength:
  long rssi = WiFi.RSSI();
  Serial.print("signal strength (RSSI):");
  Serial.print(rssi);
  Serial.println(" dBm");
}




I tried uploading the code to Arduino after plugging in the wifi shield, an error message was shown "Error opening serial port COM3"

Can anyone suggest a possible solution?

What wifi shield? What Arduino? Can you upload without the shield attached?

Arduino UNO R3 and ESP8266 Serial Wifi Expansion Board Module

See the DIP switches? You probably have them set incorrectly. Also please answer the second question of reply #3.

Which are the DIP switches?
When the Arduino is powered on, the red light on the shield turns on, which means the shield is properly connected, right?

You won't get far without reading the instructions for this combination of devices.

I have read through the documentation, checked the troubleshooting, still couldn't get a possible solution to this, the same error message is shown, can anyone help me out?

Have you verified that you have the right boards settings and serial port in the IDE upload menu?

Please supply a link to the documentation so we can help you read it. I'm sure it will identify the DIP switches and tell you how to set them. You didn't say what troubleshooting steps you followed. Please list them so we don't have to guess and ask you about them one by one.

Are you sure that this sketch is written for this type of wifi shield?

Also you haven't finished answering the questions that have been asked. That will discourage people from asking questions that might help you, since not getting answer wastes their time.

So I am now asking you for the second time,
"Can you upload without the shield attached?"