在目标 C 中测试 IP 地址的连接/可用性

Question

基本上，我希望能够检查本地网络上的特定主机是否"启动"。

当无法访问主机时，以下代码行将挂起，因此我想在运行它之前先执行检查。

    [_outputStream write:[data bytes] maxLength:[data length]];

我认为类似的

查询在以下链接中得到了回答，但我认为我需要使用CFHostCreateWithAddress而不是CFHostCreateWithName

iPhone应用程序中NSHost的替代品

这是我

尝试做的事情...

Boolean result;
struct sockaddr_in address;
address.sin_family = AF_INET;
address.sin_port = htons(80);
inet_pton(AF_INET, "192.168.1.31", &address.sin_addr);
CFDataRef sockData = CFDataCreate(NULL, &address, sizeof(address));
CFHostRef host = CFHostCreateWithAddress(NULL, sockData);
result = CFHostStartInfoResolution(host, kCFHostAddresses, NULL);
if (result == TRUE) {
    NSLog(@"Resolved");
} else {
    NSLog(@"Not resolved");
}

即使主机启动，我也没有解决。

下面是我尝试使用 Reachability 类。我的代码告诉我，尽管指定地址没有主机，但以下地址是可访问的。

struct sockaddr_in address;
address.sin_family = AF_INET;
address.sin_port = htons(80);
inet_pton(AF_INET, "192.168.1.31", &address.sin_addr);
Reachability *reachability = [Reachability reachabilityWithAddress:&address];
NetworkStatus reachabilitytoHost = [reachability currentReachabilityStatus];
if(reachabilitytoHost != NotReachable)
{
    NSLog(@"Reachable");
}
else
{
    NSLog(@"Not Reachable");
}

Answer 1

将

可达性类添加到项目中。

 #import "Reachability.h"

同时添加SystemConfiguration框架。

Reachability *reachability = [Reachability reachabilityWithHostName:@"www.example.com"];
NetworkStatus reachabilitytoHost = [reachability currentReachabilityStatus];
if(reachabilitytoHost != NotReachable)
{
    //reachable
}
else
{
    // not reachable
}

在此处检查示例代码：https://developer.apple.com/library/ios/samplecode/Reachability/Introduction/Intro.html

欲了解更多信息： https://developer.apple.com/library/ios/samplecode/Reachability/Listings/Reachability_Reachability_h.html

Answer 2

看看 Tony Million： 的 Reachability class： https://github.com/tonymillion/Reachability

来自自述文件：

    // Allocate a reachability object
Reachability* reach = [Reachability reachabilityWithHostname:@"www.google.com"];
// Set the blocks
reach.reachableBlock = ^(Reachability*reach)
{
    // keep in mind this is called on a background thread
    // and if you are updating the UI it needs to happen
    // on the main thread, like this:
    dispatch_async(dispatch_get_main_queue(), ^{
      NSLog(@"REACHABLE!");
    });
};
reach.unreachableBlock = ^(Reachability*reach)
{
    NSLog(@"UNREACHABLE!");
};
// Start the notifier, which will cause the reachability object to retain itself!
[reach startNotifier];

显然，您可以将 www.google.com 替换为要测试的任何地址。