getting 403 forbidden when access sharepoint web service from ios in swift

I am new to ios development and i am trying to access sharepoint web service from ios but i getting 403 forbidden in response

I have also refer to this link for authenticationbut it doesn't work

Then I try to authenticate using didReceiveAuthenticationChallenge method which i refer from This link

As per the developer.apple.com documentation this method is deprecated and i use willSendRequestForAuthenticationChallenge method

Following is Code

var message:String = "<?xml version='1.0' encoding='utf-8'?><soap12:Envelope xmlns:xsi='http://ift.tt/ra1lAU' xmlns:xsd='http://ift.tt/tphNwY' xmlns:soap12='http://ift.tt/18hkEkn'><soap12:Body><GetList xmlns='http://ift.tt/rrg8m0'><listName>ThemeGallery</listName></GetList></soap12:Body></soap12:Envelope>"

var urlString = "https://domainname/_vti_bin/Lists.asmx"

var url = NSURL(string: urlString)

var req = NSMutableURLRequest(URL: url!)

var msglength = String(countElements(message))

req.addValue("text/xml; charset=utf-8", forHTTPHeaderField: "Content-Type")

req.addValue(msglength, forHTTPHeaderField: "Content-Length")

req.addValue("http://ift.tt/Wiluec", forHTTPHeaderField: "SOAPAction")

req.HTTPMethod = "POST"

req.HTTPBody = message.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)

var connection = NSURLConnection(request: req, delegate: self, startImmediately: true)
connection?.start()

---

Connection Methods

func connection(connection: NSURLConnection, willSendRequestForAuthenticationChallenge challenge: NSURLAuthenticationChallenge) {
if challenge.previousFailureCount == 0
{
    var newCredential = NSURLCredential(user: self.username, password: self.password, persistence: NSURLCredentialPersistence.ForSession)
    challenge.sender.useCredential(newCredential, forAuthenticationChallenge: challenge)

}
else
{
    challenge.sender.cancelAuthenticationChallenge(challenge)

}
}

---

Parsing method

func connectionDidFinishLoading(connection: NSURLConnection!) {
var xmlParser = NSXMLParser(data: self.mutableData)

xmlParser.delegate = self
xmlParser.parse()
xmlParser.shouldResolveExternalEntities = true
}

Is there any specific rights we have to give for access web services of sharepoint