Name
Dns
Synopsis
This type offers up a collection of shared methods for resolving DNS (Domain Name Service) operations. Because raw IP addresses (such as 192.168.0.1) can be difficult for humans to remember, DNS servers take human-friendly names (such as “www.oreilly.com”) and in turn translate them into IP addresses and/or back again. This ability can be useful in a variety of scenarios, including the simple logging of clients who have visited a web site recently. (Note that this is not a secure way of tracking usage — even a simple attacker can spoof the return address of an IP packet, so don’t rely on this mechanism for any kind of security validation or audit trail.)
The GetHostByName()
method takes a hostname (such as
“www.oreilly.com”) and returns the corresponding IPHostEntry
instance — this IPHostEntry
instance is used later in
several of the System.Net
and System.Net.Sockets
types. This method (along with the paired method Resolve()
)
can be invoked asynchronously using the BeginGetHostByName()
or BeginResolve()
methods. Like all async methods in the
.NET Framework, they take two additional parameters: an AsyncCallback
object,
and a generic object
parameter that is passed to the AsyncCallback
when the
call completes.
At the surface, there would appear to be no difference between calling Resolve()
or GetHostByName()
; in fact,
the Resolve()
method calls into GetHostByName()
after doing a small amount of preprocessing to check if the string passed is either a standard host ...
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