在 MonoTouch 中使用 Bonjour NSNetService 来自 NSData 的 IPAddress？

Question

我在 iOS 上使用 Xamarin + MonoTouch 来浏览网络上的 Web 服务器，然后我可以从中下载文件。

传递给解析事件处理程序的 NSNetService 包含地址作为 NSData。我找不到将 NSData 转换为实际 IP 地址的好方法，然后我可以从中构建 URL，即 http:// /folder/file.htm

这是我的 NSNetService.AddressResolved 事件处理程序：

private void OnServiceResolved(object sender, EventArgs args)
{
        NSNetService service = (NSNetService)sender;
        // service.Port is valid.
        // service.HostName is valid.
        // but we want the IP addres, which is in service.Addresses.
        // None of the following four methods works quite right.
        IPAddress address = (IPAddress)service.Addresses [0]; // Cannot convert type NSData to IPAddress
        SocketAddress address2 = (SocketAddress)service.Addresses[0]; // Cannot convert NSData to SocketAddress. A binary copy might work?
        IPHostEntry entry = (IPHostEntry)service.Addresses [0]; // Cannot convert NSData to IPHostEntry
        IPHostEntry entry2 = Dns.GetHostByName (service.HostName); // This kinda works, but is dumb. Didn't we just resolve?
}

在解析事件中从 NSNetService 获取服务 IP 地址的正确方法是什么？

Answer 1

NSNetService.Addresses 属性为您提供 NSData 实例，这些实例必须转换为 IPAddress（或其他 .NET 类型）可以消化的东西。例如

MemoryStream ms = new MemoryStream ();
(ns.Addresses [0] as NSData).AsStream ().CopyTo (ms);
IPAddress ip = new IPAddress (ms.ToArray ());

请注意，这可能会返回一个 IPv6 地址（或IPAddress 不接受的格式）。您可能想要遍历所有Addresses 以找到最佳。

我将考虑在 Xamarin.iOS 的未来版本中添加一种便捷方法。

更新

返回IPAddress 的更完整版本如下所示：

static IPAddress CreateFrom (NSData data)
{
    byte[] address = null;
    using (MemoryStream ms = new MemoryStream ()) {
        data.AsStream ().CopyTo (ms);
        address = ms.ToArray ();
    }
    SocketAddress sa = new SocketAddress (AddressFamily.InterNetwork, address.Length);
    // do not overwrite the AddressFamily we provided
    for (int i = 2; i < address.Length; i++)
        sa [i] = address [i];
    IPEndPoint ep = new IPEndPoint (IPAddress.Any, 0);
    return (ep.Create (sa) as IPEndPoint).Address;
}