在 Objective C 中测试 IP 地址的连接性/可用性

Question

基本上我希望能够检查我本地网络上的特定主机是否“启动”。

当主机无法访问时，下面这行代码会挂起，所以我想在运行之前先进行检查。

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

我认为在以下链接中回答了类似的查询，但我认为我需要使用CFHostCreateWithAddress 而不是CFHostCreateWithName

Alternatives to NSHost in iPhone app

这是我正在尝试做的事情......

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，我也得到 Not resolve。

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，但可以访问以下地址。

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

将可达性类添加到您的项目中。

 #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
}

在此处查看示例代码：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 课程：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];

您显然可以将 www.google.com 替换为您想测试的任何地址。