' 导入命名空间
Imports System.Text
Imports System.Net.Sockets
Imports System.Net.Security
Imports System.Net

Namespace Examples.NegotiateStreamExample

    Public Class ASynchronousAuthenticatingTcpClient

        Shared client As TcpClient = Nothing

        Public Shared Sub Main(args As String())
            ' Establish the remote endpoint for the socket.
            ' For this example, use the local machine.
            Dim ipHostInfo = Dns.GetHostEntry("localhost")
            Dim ipAddress = ipHostInfo.AddressList(0)

            ' Client and server use port 11000. 
            Dim remoteEP As New IPEndPoint(ipAddress, 11000)

            ' Create a TCP/IP socket.
            client = New TcpClient()

            ' Connect the socket to the remote endpoint.
            client.Connect(remoteEP)
            Console.WriteLine("Client connected to {0}.", remoteEP.ToString())

            ' Ensure the client does not close when there is 
            ' still data to be sent to the server.
            client.LingerState = (New LingerOption(True, 0))

            ' Request authentication.
            Dim clientStream = client.GetStream()
            Dim authStream As New NegotiateStream(clientStream, False)

            ' Pass the NegotiateStream as the AsyncState object 
            ' so that it is available to the callback delegate.
            Dim ar = authStream.BeginAuthenticateAsClient(
                New AsyncCallback(AddressOf EndAuthenticateCallback), authStream)

            Console.WriteLine("Client waiting for authentication...")

            ' Wait until the result is available.
            ar.AsyncWaitHandle.WaitOne()

            ' Display the properties of the authenticated stream.
            AuthenticatedStreamReporter.DisplayProperties(authStream)

            ' Send a message to the server.
            ' Encode the test data into a byte array.
            Dim message = Encoding.UTF8.GetBytes("Hello from the client.")
            ar = authStream.BeginWrite(message, 0, message.Length, 
                New AsyncCallback(AddressOf EndWriteCallback), authStream)
            ar.AsyncWaitHandle.WaitOne()
            Console.WriteLine("Sent {0} bytes.", message.Length)

            ' Close the client connection.
            authStream.Close()
            Console.WriteLine("Client closed.")

        End Sub

        ' The following method is called when the authentication completes.
        Public Shared Sub EndAuthenticateCallback(ar As IAsyncResult)

            Console.WriteLine("Client ending authentication...")
            Dim authStream = CType(ar.AsyncState, NegotiateStream)
            Console.WriteLine("ImpersonationLevel: {0}", authStream.ImpersonationLevel)

            ' End the asynchronous operation.
            authStream.EndAuthenticateAsClient(ar)

        End Sub

        ' The following method is called when the write operation completes.
        Public Shared Sub EndWriteCallback(ar As IAsyncResult)

            Console.WriteLine("Client ending write operation...")
            Dim authStream = CType(ar.AsyncState, NegotiateStream)

            ' End the asynchronous operation.
            authStream.EndWrite(ar)

        End Sub
    End Class

    ' The following class displays the properties of an AuthenticatedStream.
    Public Class AuthenticatedStreamReporter
        Public Shared Sub DisplayProperties(stream As AuthenticatedStream)
            Console.WriteLine("IsAuthenticated: {0}", stream.IsAuthenticated)
            Console.WriteLine("IsMutuallyAuthenticated: {0}", stream.IsMutuallyAuthenticated)
            Console.WriteLine("IsEncrypted: {0}", stream.IsEncrypted)
            Console.WriteLine("IsSigned: {0}", stream.IsSigned)
            Console.WriteLine("IsServer: {0}", stream.IsServer)
        End Sub
    End Class
End Namespace