iOS客户端/服务器实现和"正在进行操作"错误

Question

背景

我一直在从各种示例代码和经典的Unix网络编程教科书中学习插座和网络编程,同时尝试将这些知识用于我正在开发的应用程序中.我目前正在处理应用程序的一部分,需要简单的客户端 - 服务器设置.

这是现在的情况(好吧,它应该如何):

1. 服务器发布自己NSNetService并使用创建套接字CFSocketCreateWithNative()
2. 客户端找到服务器 NSNetServiceBrowser
3. 客户端解析发现的服务
4. 服务器从CFSocket获取回调,它会创建一个新的class(MyConnection)实例来处理连接.用于获得连接的读写流CFStreamCreatePairWithSocket().
5. 客户端向服务器发送消息(@"hi")
6. 服务器将从客户端收到的数据发送回客户端(这是我的问题所在)
7. 客户端在UIAlertView中显示字符串

两个问题

1. 当我尝试让服务器将数据发送回客户端时,我收到"正在进行操作"错误,如下面的连接代码中所示.我相信这是因为NSOutputStream没有空间.处理这个问题的最佳方法是什么？我知道它应该等待NSStreamEventHasSpaceAvailable事件,但它似乎没有发生......
   编辑:呃......当我收到这个错误时,我只用iPhone模拟器测试应用程序,并让它充当服务器和客户端,因为我的新公寓还没有互联网:P使用两个真实设备时似乎没有问题.

2. 是否可以制作此服务器,以便从每个连接对象发送和接收数据不会阻止从其他连接对象发送和接收数据？每个新的连接对象是否需要在新的runloop或线程或类似的东西上？我已经围绕苹果并发文档进行了捕获,但没有任何内容正在跳出......目标是尽可能快地将响应发送给客户端,无论有多少其他客户端连接到服务器.
   更新:除了允许并发连接到此服务器之外,我正在考虑将连接排队并一次处理一个,因为需要发送到每个客户端的数据量非常小.这是最好的决定吗？如果队列中有数百个客户端怎么办？第二个想法,这可能是一个坏主意,因为在快速的本地网络上建立连接需要一两秒,并且需要更长时间才能使用蓝牙...我会喜欢这方面的专家建议:)

相关守则

注意:APNetService和APNetServiceBrowser类似于NSNetService和NSNetServiceBrowser

服务器代码

- (void) startServerForGroup:(NSString *)name
{
  self.groupName = name;

  NSInteger port = [self prepareListeningSocket];

  self.service = [[APNetService alloc] initWithDomain:@"local."
                                                 type:@"_example._tcp." 
                                                 name:self.groupName
                                                 port:port];
  self.service.delegate = self;
  [self.service publish];
}

- (NSInteger) prepareListeningSocket
{
  int     listenfd, err, junk, port;  
  BOOL    success;

  struct sockaddr_in addr;

  port = 0;

  listenfd = socket(AF_INET, SOCK_STREAM, 0);
  success = (listenfd != -1);

  if (success) {
    bzero(&addr, sizeof(addr));  
    addr.sin_len    = sizeof(addr);
    addr.sin_family = AF_INET;
    addr.sin_port   = 0;
    addr.sin_addr.s_addr = INADDR_ANY;
    err = bind(listenfd, (const struct sockaddr *) &addr, sizeof(addr));
    success = (err == 0);
  }
  if (success) {
    err = listen(listenfd, 5);
    success = (err == 0);
  }
  if (success) {
    socklen_t   addrLen;

    addrLen = sizeof(addr);
    err = getsockname(listenfd, (struct sockaddr *) &addr, &addrLen);
    success = (err == 0);

    if (success) {
      assert(addrLen == sizeof(addr));
      port = ntohs(addr.sin_port);
    }
  }
  if (success) {
    CFSocketContext context = { 0,(__bridge void*) self, NULL, NULL, NULL };

    CFSocketRef socket = CFSocketCreateWithNative(
                                                  NULL, 
                                                  listenfd, 
                                                  kCFSocketAcceptCallBack, 
                                                  AcceptCallback, 
                                                  &context
                                                  );
    if (socket) {
      self.listeningSocket = socket;
      CFRelease(socket);
      success = YES;
    }

    if (success) {
      CFRunLoopSourceRef  rls;

      listenfd = -1;

      rls = CFSocketCreateRunLoopSource(NULL, self.listeningSocket, 0);
      assert(rls != NULL);

      CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);

      CFRelease(rls);
    }
  }

  if ( success ) {
    return port;
  } 
  else {
    NSLog(@"FAILED TO START SERVER");

    if (listenfd != -1) {
      junk = close(listenfd);
      assert(junk == 0);
    }
    return -1;
  }
}

#pragma mark - Callback

// Called by CFSocket when someone connects to the listening socket
static void AcceptCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info)
{
  MyServer *  obj;

  obj = (__bridge MyServer *) info;

  assert(s == obj->_listeningSocket);

  MyConnection *newCon = [[MyConnection alloc] initWithFileDescriptor:*(int*)data];

  [newCon startReceive];

    //add the new connection object to the servers mutable array of connections
  [obj.connections addObject:newCon];

}

连接代码

- (void) startReceive
{
  CFReadStreamRef     readStream;
  CFWriteStreamRef    writeStream;

  CFStreamCreatePairWithSocket(NULL, self.fd, &readStream, &writeStream);

  self.inputStream =  (__bridge_transfer NSInputStream *) readStream;
  self.outputStream = (__bridge_transfer NSOutputStream*) writeStream;

  [self.inputStream setProperty:(id)kCFBooleanTrue forKey:(NSString *)kCFStreamPropertyShouldCloseNativeSocket];
  [self.outputStream setProperty:(id)kCFBooleanTrue forKey:(NSString *)kCFStreamPropertyShouldCloseNativeSocket];

  self.inputStream.delegate = self;
  self.outputStream.delegate = self;


  [self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
  [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

  [self.inputStream open];
  [self.outputStream open];
}


#pragma mark - NSStreamDelegate

- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
  switch (eventCode) {

    case NSStreamEventHasBytesAvailable: {
      NSInteger       bytesRead;
      uint8_t         buffer[32768];

      bytesRead = [self.inputStream read:buffer maxLength:sizeof(buffer)];
      if (bytesRead == -1)...
      else if (bytesRead == 0)...
      else {
                NSData  *data = [NSData dataWithBytes:buffer length:bytesRead];
                [self didReceiveData:data];
      }
    } break;
    case NSStreamEventHasSpaceAvailable: {
      self.space = YES;
    } break;

    . . .
  }
}

- (void) didReceiveData:(NSData *)data
{
  if (self.space) 
    NSLog(@"SPACE");
  else
    NSLog(@"NO SPACE"); //this gets printed

  NSInteger i = [self.outputStream write:data.bytes maxLength:data.length];

  if (i < 0) {
    printf("%s",strerror(errno)); //"Operation now in progress" error
  }  
}

客户代码

#pragma mark - APNetServiceBrowserDelegate

- (void) browser:(APNetServiceBrowser *)browser didAddService:(APNetService *)service moreComing:(BOOL)moreComing
{
        //omitting checks that determine which server to connect to, if multiple

    service.delegate = self;
    [service resolveWithTimeout:20]; 
}


#pragma mark - APNetServiceDelegate

- (void) netServiceDidResolveAddress:(APNetService *)service
{    
  NSInputStream   *input; 
  NSOutputStream  *output;

  [service getInputStream:&input outputStream:&output];

  self.inputStream = input;
  self.outputStream = output;

  self.inputStream.delegate = self;
  self.outputStream.delegate = self;

  [self.inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
  [self.outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];

  [self.inputStream open];
  [self.outputStream open];
}


#pragma mark - NSStreamDelegate

- (void) stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
    switch (eventCode) {      

    case NSStreamEventHasBytesAvailable: {
      NSInteger       bytesRead;
      uint8_t         buffer[32768];

      bytesRead = [self.inputStream read:buffer maxLength:sizeof(buffer)];

      if (bytesRead == -1) NSLog(@"Error reading data");
      else if (bytesRead == 0) NSLog(@"no bytes read");
      else {
                NSData  *data = [NSData dataWithBytes:buffer length:bytesRead];
                [self didReceiveData:data];
      }
    } break;

    case NSStreamEventHasSpaceAvailable: {
      if (!self.isWaitingForReply) {
        [self sendHelloMessage];
      }
    } break;
        //omitted other NSStreamEvents    
  }
}

- (void) sendHelloMessage
{
  NSData *d = [NSKeyedArchiver archivedDataWithRootObject:@"hi"];

  [self.outputStream write:d.bytes maxLength:d.length];
  self.isWaiting = YES;
}


- (void) didReceiveData:(NSData *)data
{
  NSString  *string = [NSKeyedUnarchiver unarchiveObjectWithData:data];

  UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Message" 
                                                  message:string
                                                 delegate:self
                                        cancelButtonTitle:@"OK"
                                        otherButtonTitles:nil];
  [alert show];
}

Answer 1

据我所知，您希望创建一个可以非常快速地处理许多连接的服务器。c10k 页面是一个很好的起点文档： http: //www.kegel.com/c10k.html。是的，排队可能是一个好主意，它比分叉消耗的资源少得多，并且响应速度更快。然而，这也意味着您的计算量保持相对较小，因此您仍然能够快速回复。也许是一个好的开始http://libevent.org/，检查它是如何做到的，它是为这种用途而设计的。

祝你好运。