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PowerTCP SSL Sockets for .NET |
| Dart.PowerTCP.SslSockets Namespace > Dns Class : BeginGetHost Method |
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PowerTCP SSL Sockets for .NET |
| Dart.PowerTCP.SslSockets Namespace > Dns Class : BeginGetHost Method |
Asynchronously resolve a host name to a dot address or a dot address to a host name.
[Visual Basic]
<DescriptionAttribute("Begin an asynchronous name or IP address resolution.")>
Public Function BeginGetHost( _
ByVal host As String, _
ByVal state As Object _
) As IAsyncResult[C#]
[DescriptionAttribute("Begin an asynchronous name or IP address resolution.")]
public IAsyncResult BeginGetHost(
string host,
object state
);[C++]
[DescriptionAttribute("Begin an asynchronous name or IP address resolution.")]
public: IAsyncResult* BeginGetHost(
string* host,
Object* state
) [C++/CLI]
[DescriptionAttribute("Begin an asynchronous name or IP address resolution.")]
public:
IAsyncResult^ BeginGetHost(
String^ host,
Object^ state
) An IAsyncResult that represents the asynchronous operation, which could still be pending.
| Exception | Description |
|---|---|
| SocketException | No DNS server was specified. |
| InvalidOperationException | BeginXXX method used without providing an EndXXX event handler. |
This method provides both asynchronous forward lookup (resolve a host name to an address) and asynchronous reverse lookup (resolve an address to a host name). When the lookup completes, the EndGetHost event is raised. Made available in this event is a DnsEventArgs which describes the response from the DNS server.
When host is a DNS-style host name associated with multiple IP addresses, only the first IP address that resolves to that host name is returned.
To resolve an email address asynchronously, use BeginGetMailHosts. To resolve a host name or a dot address synchronously, use GetHost.
The following example demonstrates using the Dns control to asynchronously resolve a domain name.
[Visual Basic]
Private Sub AsynchResolveTest()
Dns1.Server = "206.64.128.5"
Dns1.BeginGetHost("www.dart.com", Nothing)
End Sub
Private Sub Dns1_EndGetHost(ByVal sender As Object, ByVal e As DnsEventArgs) Handles Dns1.EndGetHost
' Check for any exceptions that occurred
If e.Exception Is Nothing Then
DisplayResult(e.Host)
End If
End Sub
Private Sub DisplayResult(ByVal result As System.Net.IPHostEntry)
' Display host name
Debug.WriteLine("Host name: " + result.HostName)
' Display addresses, if any
Dim add As System.Net.IPAddress
For Each add In result.AddressList
Debug.WriteLine("Address: " + add.ToString())
Next
' Display aliases, if any
Dim s As String
For Each s In result.Aliases
Debug.WriteLine("Aliases: " + s)
Next
End Sub
[C#]
private void AsynchResolveTest()
{
dns1.Server = "206.64.128.5";
dns1.BeginGetHost("www.dart.com", null);
}
private void dns1_EndGetHost(object
sender, DnsEventArgs e)
{
// Check for any exceptions that occurred
if(e.Exception == null)
{
DisplayResult(e.Host);
}
}
private void DisplayResult(System.Net.IPHostEntry result)
{
// Display host name
Debug.WriteLine("Host name: " + result.HostName);
// Display addresses, if any
foreach(System.Net.IPAddress add in result.AddressList)
Debug.WriteLine("Address: " + add.ToString());
// Display aliases, if any
foreach(string s in result.Aliases)
Debug.WriteLine("Aliases: " + s);
}
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family
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Documentation version 1.1.2.0.
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