Aufruf JSON web-service mit Parameter - Objective C - iOS

Ich versuche zu nennen, eine einfache JSON-webservice mit einem parameter in objective-c. Nicht funktioniert so weit.

Hier ist die web-service-Methode:

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public void LogIn(string username, string password)
{
    Context.Response.Write(username + "___" + password);
    Context.Response.End();
}

Hier ist meine Objective-C-code:

//Build dictionnary with parameters
NSString *username = @"usernameTest";
NSString *password = @"passwordTest";
NSMutableDictionary *dictionnary = [NSMutableDictionary dictionary];
[dictionnary setObject:username forKey:@"username"];
[dictionnary setObject:password forKey:@"password"];

NSError *error = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionnary
                                                   options:kNilOptions
                                                     error:&error];   

NSString *urlString = @"http://localhost:8080/ListrWS.asmx/LogIn";
NSURL *url = [NSURL URLWithString:urlString];

//Prepare the request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];
[request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request setValue:@"json" forHTTPHeaderField:@"Data-Type"];
[request setValue:[NSString stringWithFormat:@"%d", [jsonData length]]  forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:jsonData];    

NSError *errorReturned = nil;
NSURLResponse *theResponse =[[NSURLResponse alloc]init];
NSData *data = [NSURLConnection sendSynchronousRequest:request
                                     returningResponse:&theResponse
                                                 error:&errorReturned];
if (errorReturned) 
{
    //...handle the error
}
else 
{
    NSString *retVal = [[NSString alloc] initWithData:data
                                             encoding:NSUTF8StringEncoding];
    NSLog(@"%@", retVal);

}

Hier ist was:

NSLog(@"%@", retVal);

display:

{"Message":"Thread was being aborted.","StackTrace":"   at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)\r\n   

at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)\r\n   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)\r\n
at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)\r\n   at System.Web.Script.Services.WebServiceMethodData.CallMethod(Object target, IDictionary`2 parameters)\r\n at
System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)\r\n   at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.Threading.ThreadAbortException"}

Irgendwelche Ideen ?