关于同步post上传参数的问题

.h文件#import 

@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet UITextField *username;

@property (weak, nonatomic) IBOutlet UITextField *pwd;
(IBAction)signin:(id)sender;

@end
 .m文件中的按钮方法- (IBAction)signin:(id)sender {
NSURL *url = [NSURL URLWithString:@"http://14.17.84.128:8088/wcf/ActionService.svc/action/web/get/do?jsoncallback=?"];

//创建请求

NSMutableURLRequest *request = [[NSMutableURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10];

[request setHTTPMethod:@"POST"];

NSString *str = @"ActionCode =0x2001¶meter=pwd###123#####userNo###aaa& LoginID=&LoginIp=";//设置参数

NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];

[request setHTTPBody:data];

//连接服务器



NSData *received = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];



NSString *str1 = [[NSString alloc]initWithData:received encoding:NSUTF8StringEncoding];



NSLog(@"%@",str1);


}

在上传参数的时候，我应该怎样子才能让上传参数中的123和aaa两个参数变成我在textfield中输入的参数呢？就是用文本框中输入的参数写入到post的参数中。