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的iOS客户端/服务器实现与“操作正在进行”错误

分类: 技术问答 • 2022-08-15 12:23:38
问题描述：

背景

我一直有种自学约插座和各种示例代码网络编程和经典UNIX网络编程教科书，同时努力把知识工作在我现在正在开发的应用程序中。我目前正在研究需要简单的客户端 - 服务器设置的应用程序的一部分。的iOS客户端/服务器实现与“操作正在进行”错误

这是怎么一回事呢，现在（当然，它应该怎么走）：

  1. Server发布本身NSNetService并创建使用CFSocketCreateWithNative()
  2. 客户端的插座中找到与NSNetServiceBrowser
  3. 客户端解析服务器发现的服务
  4. 服务器从CFSocket获取一个回调，该CFSocket创建一个类的新实例（MyConnection）来处理连接。读取和写入连接的流可通过CFStreamCreatePairWithSocket()获得。
  5. 的客户机消息的服务器（@“HI”）
  6. 服务器发送其从客户端接收返回给客户端（这是我的问题是）
  7. 客户端显示字符串中所涉及的数据UIAlertView中

两个问题

  1. 我收到“操作正在进行”的错误，当我尝试让服务器将数据发送回客户端，如连接代码注释下方。我相信这是因为NSOutputStream没有可用的空间。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：咄......当我收到此错误只与iPhone模拟器我测试的应用程序，并让它充当服务器和客户端，因为我还没有在我的新公寓中使用互联网：P使用两台真实设备似乎不成问题。

  2. 是否有可能使这种服务器，以便发送和从每个连接对象接收数据的不阻塞发送和从其他连接对象接收数据的？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？我围绕苹果并发性文档钓鱼，但没有什么是跳出来的......目标是尽可能快地向客户端发送回复，无论有多少其他客户端连接到服务器。
    更新：在允许到该服务器的并发连接，我只考虑排队的连接和处理它们一次一个，因为数据需要被发送到每个客户端的量非常小的代替。这是最好的决定吗？如果队列中有数百个客户端会怎么样？第二个想法，这可能是一个坏主意，因为连接的建立在快速的本地网络上需要一两秒钟，而蓝牙需要更长的时间......我希望在这个问题上:)

相关代码

注意一些专家的意见：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 
    } 
}

客户端代码

#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]; 
}
+0

+1，结构良好！ – doNotCheckMyBlog

答

正如从我所看到的，你想，可以处理很多连接速度非常快的服务器。一个很好的起点文档是c10k页面：http://www.kegel.com/c10k.html。排队可能是一个好主意，它将消耗比分支更少的资源，并且会更快地响应。但是，这也意味着您的计算保持相对较小，以便您仍然能够快速回复。一个好的开始也许http://libevent.org/，检查它是如何做到的，它是这种用途的设计。

祝你好运。

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