C# - IPv4, IPv6를 모두 지원하는 서버 소켓 생성 방법
코드는 다음과 같이 간단합니다.
using (Socket sock = new Socket(SocketType.Stream, ProtocolType.Tcp))
{
sock.Bind(new IPEndPoint(IPAddress.IPv6Any, 9982));
// ...[생략]...
}
보통 Socket 생성자에 AddressFamily를 함께 지정하는데요,
// IPv4
Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
// IPv6
Socket sock = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
(.NET 4.5부터 지원하는) 저걸 생략한 소켓 생성자의 경우,
public Socket(SocketType socketType, ProtocolType protocolType)
: this(OSSupportsIPv6 ? AddressFamily.InterNetworkV6 : AddressFamily.InterNetwork, socketType, protocolType)
{
if (OSSupportsIPv6)
{
DualMode = true;
}
}
보는 바와 같이 운영체제가 IPv6를 지원하는 경우라면 기본적으로 InterNetworkV6로 초기화가 됩니다. 그러면서 동시에 (.NET 4.5부터 지원하는)
DualMode 속성이 true로 바뀌는데요,
// NOTE: on *nix, the OS IP stack changes a dual-mode socket back to a
// normal IPv6 socket once the socket is bound to an IPv6-specific
// address. This can cause behavioral differences in code that checks
// the value of DualMode (e.g. the checks in CanTryAddressFamily).
public bool DualMode
{
get
{
if (AddressFamily != AddressFamily.InterNetworkV6)
{
return false;
}
return ((int)GetSocketOption(SocketOptionLevel.IPv6, SocketOptionName.IPv6Only)! == 0);
}
set
{
if (AddressFamily != AddressFamily.InterNetworkV6)
{
throw new NotSupportedException(SR.net_invalidversion);
}
SetSocketOption(SocketOptionLevel.IPv6, SocketOptionName.IPv6Only, value ? 0 : 1);
}
}
즉, SocketOptionName.IPv6Only 옵션을 끄는 역할을 합니다. only 옵션을 껐다는 것은 IPv6/IPv4 듀얼 모드로 동작한다는 것을 의미합니다. 간단하죠? ^^ 따라서 위와 같이 소켓을 생성하는 것은 다음과 같이 바꿔서 표현할 수도 있습니다.
using (Socket sock = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp))
{
// Dual Mode Sockets – Never create an IPv4 Socket again
// https://devblogs.microsoft.com/dotnet/dual-mode-sockets-never-create-an-ipv4-socket-again/
sock.DualMode = true;
sock.Bind(new IPEndPoint(IPAddress.IPv6Any, 9982));
// ...[생략]...
}
기왕이면 코드가 단순한 것이 좋으니 첫 번째 유형으로 쓰고, 단지 그것이 어떤 의미인지만 이 글을 통해 알아두시면 되겠습니다. ^^
참고로, DualMode는 Vista 이후의 운영체제에서만 지원됩니다. 만약 Vista 미만의 운영체제를 지원해야 한다면 IPv4, IPv6 소켓을 각각 생성해 바인딩시켜야 합니다.
IPv6 소켓을 사용하면서 주소는 IPv4를 지정하면,
Socket sock = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
sock.Bind(new IPEndPoint(IPAddress.Any, 18000));
이런 오류가 발생합니다.
Unhandled exception. System.Net.Sockets.SocketException (10014): The system detected an invalid pointer address in attempting to use a pointer argument in a call.
at System.Net.Sockets.Socket.UpdateStatusAfterSocketErrorAndThrowException(SocketError error, String callerName)
at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Bind(EndPoint localEP)
...[생략]...
DualMode 속성을 지원하지 않는 .NET 4.5 미만에서는 이렇게!
Tired of creating sockets for each protocol, to make your application listen on all addresses for a given port?
; https://web.archive.org/web/20130909044601/http://blogs.msdn.com/b/malarch/archive/2005/11/18/494769.aspx
There is no more pain. Here is a cool new feature supported in Vista and Windows Server Longhorn. By just setting a socketoption, you will be able to use the same socket to accept connections from both ipv4 and ipv6 clients.
The following sample code shows how to configure the server socket.
static void Main(string[] args)
{
Socket sock = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp);
sock.SetSocketOption(SocketOptionLevel.IPv6, (SocketOptionName)27, 0);
sock.Bind(new IPEndPoint(IPAddress.IPv6Any, 8000));
sock.Listen(4);
Socket client = sock.Accept();
Console.WriteLine("Client has connected successfully with the server");
}
Create an IPv6 socket. Set the socket option IPV6_V6Only to false (by default it is true), to enable the socket to accept connections from ipv4 addresses too. Bind and Listen as usual. Now both ipv4 and ipv6 clients can connect to it
More info can be found in
http://www.ietf.org/rfc/rfc3493.txt.
This is because Vista has a completely redesigned TCP/IP stack.
Whereas Windows XP and Win2k3 have a dual stack architecture, i.e., the Tcp, Udp layer is separate for both ipv4 and ipv6 protocols, Vista supports the dual IP layer architecture. That is, Only a single Tcp, Udp layer is present for both the ipv4 and ipv6 protocols.
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