NSString *postString = [NSString stringWithFormat:@"username="tango"&password="charlie""];

NSLog(@"%@",postString);
//encode post string in supported encoding format in post data
postData = [postString dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];

if(connection)
  return YES;
else
  return NO;

[NSMutableRequest setHTTPRequest:urlString];

[request setURL:url];

//set HTTP method Post
[request setHTTPMethod:@"POST"];

//set HTTP header field with length of post data
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];

//set encoding value for HTTP header field
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];

 //set HTTP body or url request with postData
 [request setHTTPBody:postData];