在一个ios应用中我使用socket第三方库 AsyncSocket来实现手机客户端和PC服务器端的通信。服务器可以收到客户端发来信息，也有返回信息，但是客户端却没有收到这个返回的信息，这个为什么呢？下面是一部分代码

import "ViewController.h"

@implementation ViewController
@synthesize socket;
@synthesize host;
@synthesize message;
@synthesize port;
@synthesize status;
@synthesize button;

• (void)didReceiveMemoryWarning
  {

  [super didReceiveMemoryWarning];
  // Release any cached data, images, etc that aren't in use.

  }

#pragma mark - View lifecycle
-(void)addText:(NSString *)str
{

 status.text = [status.text stringByAppendingFormat:@"%@\n",str];

}

• (void)viewDidLoad
  {

  [super viewDidLoad];
  host.text = @"61.191.200.214";
  port.text = @"9631";
  
  [button setTitle:@"连接" forState:UIControlStateNormal];

  }

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{

 [textField resignFirstResponder];
 return YES;

}

• (void)viewDidUnload
  {
  [self setHost:nil];
  [self setMessage:nil];
  [self setStatus:nil];
  [self setPort:nil];
  [super viewDidUnload];
  }
• (void)viewWillAppear:(BOOL)animated
  {
  [super viewWillAppear:animated];
  }
• (void)viewDidAppear:(BOOL)animated
  {
  [super viewDidAppear:animated];
  }
• (void)viewWillDisappear:(BOOL)animated
  {
  [super viewWillDisappear:animated];
  }
• (void)viewDidDisappear:(BOOL)animated
  {
  [super viewDidDisappear:animated];
  }
• (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
  {
  return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
  }

-(void)socket:(GCDAsyncSocket )sock didConnectToHost:(NSString )host port:(uint16_t)port
{

 [self addText:[NSString stringWithFormat:@"连接到:%@",host]];
 [socket readDataWithTimeout:-1 tag:0];

}

• (void)socketDidDisconnect:(GCDAsyncSocket )sock withError:(NSError )err
  {

}

• (IBAction)send:(id)sender { //开始按钮
  //连接服务器端
  socket = [[GCDAsyncSocket alloc]initWithDelegate:self delegateQueue:dispatch_get_main_queue()];
  NSError *err = nil;
  if(![socket connectToHost:host.text onPort:[port.text intValue] error:&err])
  {

   [self addText:err.description];

  }else
  {

   [self addText:[NSString stringWithFormat: @"打开%@端口",socket.localHost]];

  }

  //发送数据
  if (message.text.length!=0){

   NSString* str_send=[[NSString alloc] initWithString:[NSString stringWithFormat:@"send%@",message.text]];
   [socket writeData:[str_send dataUsingEncoding:NSUTF8StringEncoding] withTimeout:-1 tag:-1];
   [self addText:[NSString stringWithFormat:@"发送:%@",message.text]];
       

  }else{

   NSString* str_send= @"receive";
   [socket writeData:[str_send dataUsingEncoding:NSUTF8StringEncoding] withTimeout:-1 tag:-1];
   [message resignFirstResponder];
   [socket readDataWithTimeout:-1 tag:0];

  }
  }

-(void)socket:(GCDAsyncSocket )sock didReadData:(NSData )data withTag:(long)tag
{

 NSString *receive = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
 [self addText:[NSString stringWithFormat:@"%@:%@",sock.connectedHost,receive]];
 [socket readDataWithTimeout:-1 tag:0];

}

@end