Windows-Linux-Mac上的UDP套接字网络断开连接行为

2 回答

• 1

  当我遇到这个问题时，我的解决方案是安排在网络配置发生变化时从操作系统获取通知 . 当我的程序收到该通知时，它将等待几秒钟（希望确保网络配置已完成更改），然后拆除并重建其所有套接字 . 这很痛苦，但似乎运作得很好 .

  当然，当网络配置发生变化时，没有与操作系统无关的方式（我知道）从操作系统获得通知，因此我必须在每个操作系统下以不同方式实现它 .

  对于MacOS / X，我产生了一个单独的watch-the-network-config线程，如下所示：

  #include <SystemConfiguration/SystemConfiguration.h>
  
  void MyNetworkThreadWatcherFunc(void *)
  {
     SCDynamicStoreRef storeRef = NULL;
     CFRunLoopSourceRef sourceRef = NULL;
     if (CreateIPAddressListChangeCallbackSCF(IPConfigChangedCallback, this, &storeRef, &sourceRef) == noErr)
     {
        CFRunLoopAddSource(CFRunLoopGetCurrent(), sourceRef, kCFRunLoopDefaultMode);
  
        while(_threadKeepGoing)   // may be set to false by main thread at shutdown time
        {
           CFRunLoopRun();
        }
  
        // cleanup time:  release our resources
        CFRunLoopRemoveSource(CFRunLoopGetCurrent(), sourceRef, kCFRunLoopDefaultMode);
        CFRelease(storeRef);
        CFRelease(sourceRef);
      }
   }
  

  还有这个设置/支持代码，从上面的函数调用：

  static OSStatus MoreSCError(const void *value) {return MoreSCErrorBoolean(value != NULL);}
  static OSStatus CFQError(CFTypeRef cf) {return (cf == NULL) ? -1 : noErr;}
  static void CFQRelease(CFTypeRef cf) {if (cf != NULL) CFRelease(cf);}
  
  // Create a SCF dynamic store reference and a corresponding CFRunLoop source.  If you add the
  // run loop source to your run loop then the supplied callback function will be called when local IP
  // address list changes.
  static OSStatus CreateIPAddressListChangeCallbackSCF(SCDynamicStoreCallBack callback, void *contextPtr, SCDynamicStoreRef *storeRef, CFRunLoopSourceRef *sourceRef)
  {
     OSStatus                err;
     SCDynamicStoreContext   context = {0, NULL, NULL, NULL, NULL};
     SCDynamicStoreRef       ref = NULL;
     CFStringRef             patterns[2] = {NULL, NULL};
     CFArrayRef              patternList = NULL;
     CFRunLoopSourceRef      rls = NULL;
  
     // Create a connection to the dynamic store, then create
     // a search pattern that finds all entities.
     context.info = contextPtr;
     ref = SCDynamicStoreCreate(NULL, CFSTR("AddIPAddressListChangeCallbackSCF"), callback, &context);
     err = MoreSCError(ref);
     if (err == noErr)
     {
        // This pattern is "State:/Network/Service/[^/]+/IPv4".
        patterns[0] = SCDynamicStoreKeyCreateNetworkServiceEntity(NULL, kSCDynamicStoreDomainState, kSCCompAnyRegex, kSCEntNetIPv4);
        err = MoreSCError(patterns[0]);
        if (err == noErr)
        {
           // This pattern is "State:/Network/Service/[^/]+/IPv6".
           patterns[1] = SCDynamicStoreKeyCreateNetworkServiceEntity(NULL, kSCDynamicStoreDomainState, kSCCompAnyRegex, kSCEntNetIPv6);
           err = MoreSCError(patterns[1]);
        }
     }
  
     // Create a pattern list containing just one pattern,
     // then tell SCF that we want to watch changes in keys
     // that match that pattern list, then create our run loop
     // source.
     if (err == noErr)
     {
         patternList = CFArrayCreate(NULL, (const void **) patterns, 2, &kCFTypeArrayCallBacks);
         err = CFQError(patternList);
     }
     if (err == noErr) err = MoreSCErrorBoolean(SCDynamicStoreSetNotificationKeys(ref, NULL, patternList));
     if (err == noErr)
     {
         rls = SCDynamicStoreCreateRunLoopSource(NULL, ref, 0);
         err = MoreSCError(rls);
     }
  
     // Clean up.
     CFQRelease(patterns[0]);
     CFQRelease(patterns[1]);
     CFQRelease(patternList);
     if (err != noErr)
     {
        CFQRelease(ref);
        ref = NULL;
     }
     *storeRef = ref;
     *sourceRef = rls;
  
     return err;
  }
  
  
  static void IPConfigChangedCallback(SCDynamicStoreRef /*store*/, CFArrayRef /*changedKeys*/, void *info)
  {
     printf("Network config changed!  Place code here to send a notification to your main thread, telling him to close and recreate his sockets....\n");
  }
  

  在Linux下（使用套接字（AF_NETLINK，SOCK_RAW，NETLINK_ROUTE）））和Windows（使用NotifyAddrChange（））获取网络配置更改通知的等效（也是相当模糊）机制，如果它们是，我可以发布很有帮助，但如果您只对MacOS / X解决方案感兴趣，我不想太多垃圾邮件 .

  回复于 2024-05-04T03:08:59+08:00
• 0

  我认为在Windows中发生的事情是，即使断开电缆连接，Windows仍然保持以太网接口打开，因为您连接了一些套接字，并且您要发送的multicast_address保持有效 . Windows也可能会更改发送方/接收方正在使用的接口，因此更改在套接字级别是透明的 .

  我认为在OS X中发生的事情是，当您断开电缆时，发送器会多播到环回接口，但接收器仍然连接到断开的以太网接口 . OS X也可能正在配置发送方发送给的自我分配的IP，但接收方仍在侦听旧的DHCP IP .

  在Linux中，当您断开电缆连接时，以太网接口会失去它's IPv4 address, removes routes to 239.255.0.1, the loopback interface isn' t配置为发送任何内容在127 ... *之外，所以你得到一个错误 .

  也许解决方案是定期重新加入OS X接收器上的组？ （也许你还需要定期重建发送者的 endpoints . ）

  另一件事是在OS X上使用自我分配的IP，因此在连接或断开电缆时，您具有相同的IP和路由 .

  回复于 2024-05-04T03:08:59+08:00