Microsoft Tutorial Question SslStream Listener_Client

Question

My question(s) are:

1. Am I making any file to replace Arg(0)? ; Instead of Arg(0), Arg(filepath\name) with the listener? Self Validating Certificate????
2. Similar with Arg(1) in the client example ; am I entering the IP to replace the Arg(1) as Arg(IPaddress)?

I plan to convert the code to webforms and send/receive certificate signed encrypted messages(strings) between my desktop and my laptop. I bought a public IP and writing an end to end encrypted content management system in theory. Just getting the console version actively listening/receiving as two apps would be a great start.

Here is a link to a console app how to for sslstream in net5/VB.
system.net.security.sslstream

The actual example(s):

Imports System.Collections  
Imports System.Net  
Imports System.Net.Sockets  
Imports System.Net.Security  
Imports System.Security.Authentication  
Imports System.Text  
Imports System.Security.Cryptography.X509Certificates  
Imports System.IO  
  
Namespace Examples.System.Net  
    Public NotInheritable Class SslTcpServer  
        Shared serverCertificate As X509Certificate = Nothing  
  
        ' The certificate parameter specifies the name of the file   
        ' containing the machine certificate.  
        Public Shared Sub RunServer(certificate As String)  
            serverCertificate = X509Certificate.CreateFromCertFile(certificate)  
            ' Create a TCP/IP (IPv4) socket And listen for incoming connections.  
            Dim listener = New TcpListener(IPAddress.Any, 8080)  
            listener.Start()  
  
            While True  
                Console.WriteLine("Waiting for a client to connect...")  
                ' Application blocks while waiting for an incoming connection.  
                ' Type CNTL-C to terminate the server.  
                Dim client As TcpClient = listener.AcceptTcpClient()  
                ProcessClient(client)  
            End While  
        End Sub  
        Private Shared Sub ProcessClient(client As TcpClient)  
            ' A client has connected. Create the   
            ' SslStream using the client's network stream.  
            Dim sslStream = New SslStream(client.GetStream(), False)  
  
            Try  
  
                sslStream.AuthenticateAsServer(serverCertificate, clientCertificateRequired:=False, checkCertificateRevocation:=True)  
                ' Display the properties And settings for the authenticated stream.  
                DisplaySecurityLevel(sslStream)  
                DisplaySecurityServices(sslStream)  
                DisplayCertificateInformation(sslStream)  
                DisplayStreamProperties(sslStream)  
  
                ' Set timeouts for the read and write to 5 seconds.  
                sslStream.ReadTimeout = 5000  
                sslStream.WriteTimeout = 5000  
  
                ' Read a message from the client.     
                Console.WriteLine("Waiting for client message...")  
                Dim messageData As String = ReadMessage(sslStream)  
                Console.WriteLine("Received: {0}", messageData)  
  
                ' Write a message to the client.  
                Dim message As Byte() = Encoding.UTF8.GetBytes("Hello from the server.<EOF>")  
                Console.WriteLine("Sending hello message.")  
                sslStream.Write(message)  
            Catch e As AuthenticationException  
                Console.WriteLine("Exception: {0}", e.Message)  
  
                If e.InnerException IsNot Nothing Then  
                    Console.WriteLine("Inner exception: {0}", e.InnerException.Message)  
                End If  
  
                Console.WriteLine("Authentication failed - closing the connection.")  
                sslStream.Close()  
                client.Close()  
                Return  
            Finally  
                ' The client stream will be closed with the sslStream  
                ' because we specified this behavior when creating  
                ' the sslStream.  
                sslStream.Close()  
                client.Close()  
            End Try  
        End Sub  
  
        Private Shared Function ReadMessage(sslStream As SslStream) As String  
  
            ' Read the  message sent by the client.  
            ' The client signals the end of the message using the  
            ' "<EOF>" marker.  
            Dim buffer As Byte() = New Byte(2048) {}  
            Dim messageData As StringBuilder = New StringBuilder()  
            Dim bytes As Integer = -1  
  
            Do  
                ' Read the client's test message.  
                bytes = sslStream.Read(buffer, 0, buffer.Length)  
  
                ' Use decoder class to convert from bytes to UTF8  
                ' in case a character spans two buffers.  
                Dim decoder As Decoder = Encoding.UTF8.GetDecoder()  
                Dim chars As Char() = New Char(decoder.GetCharCount(buffer, 0, bytes) - 1) {}  
                decoder.GetChars(buffer, 0, bytes, chars, 0)  
                messageData.Append(chars)  
  
                ' Check for EOF or an empty message.  
                If messageData.ToString().IndexOf("<EOF>") <> -1 Then  
                    Exit Do  
                End If  
            Loop While bytes <> 0  
  
            Return messageData.ToString()  
        End Function  
  
        Private Shared Sub DisplaySecurityLevel(stream As SslStream)  
            Console.WriteLine("Cipher: {0} strength {1}", stream.CipherAlgorithm, stream.CipherStrength)  
            Console.WriteLine("Hash: {0} strength {1}", stream.HashAlgorithm, stream.HashStrength)  
            Console.WriteLine("Key exchange: {0} strength {1}", stream.KeyExchangeAlgorithm, stream.KeyExchangeStrength)  
            Console.WriteLine("Protocol: {0}", stream.SslProtocol)  
        End Sub  
  
        Private Shared Sub DisplaySecurityServices(stream As SslStream)  
            Console.WriteLine("Is authenticated: {0} as server? {1}", stream.IsAuthenticated, stream.IsServer)  
            Console.WriteLine("IsSigned: {0}", stream.IsSigned)  
            Console.WriteLine("Is Encrypted: {0}", stream.IsEncrypted)  
        End Sub  
  
        Private Shared Sub DisplayStreamProperties(stream As SslStream)  
            Console.WriteLine("Can read: {0}, write {1}", stream.CanRead, stream.CanWrite)  
            Console.WriteLine("Can timeout: {0}", stream.CanTimeout)  
        End Sub  
  
        Private Shared Sub DisplayCertificateInformation(stream As SslStream)  
            Console.WriteLine("Certificate revocation list checked: {0}", stream.CheckCertRevocationStatus)  
            Dim localCertificate As X509Certificate = stream.LocalCertificate  
  
            If stream.LocalCertificate IsNot Nothing Then  
                Console.WriteLine("Local cert was issued to {0} and is valid from {1} until {2}.", localCertificate.Subject, localCertificate.GetEffectiveDateString(), localCertificate.GetExpirationDateString())  
            Else  
                Console.WriteLine("Local certificate is null.")  
            End If  
  
            ' Display the properties of the client's certificate.  
            Dim remoteCertificate As X509Certificate = stream.RemoteCertificate  
  
            If stream.RemoteCertificate IsNot Nothing Then  
                Console.WriteLine("Remote cert was issued to {0} and is valid from {1} until {2}.", remoteCertificate.Subject, remoteCertificate.GetEffectiveDateString(), remoteCertificate.GetExpirationDateString())  
            Else  
                Console.WriteLine("Remote certificate is null.")  
            End If  
        End Sub  
  
        Private Shared Sub DisplayUsage()  
            Console.WriteLine("To start the server specify:")  
            Console.WriteLine("serverSync certificateFile.cer")  
            Environment.[Exit](1)  
        End Sub  
  
        Public Shared Function Main(ByVal args As String()) As Integer  
            Dim certificate As String  
  
            If args Is Nothing OrElse args.Length < 1 Then  
                DisplayUsage()  
            End If  
  
            certificate = args(0)  
            RunServer(certificate)  
            Return 0  
        End Function  
    End Class  
End Namespace  

The Client:

Imports System.Collections  
Imports System.Net  
Imports System.Net.Security  
Imports System.Net.Sockets  
Imports System.Security.Authentication  
Imports System.Text  
Imports System.Security.Cryptography.X509Certificates  
Imports System.IO  
  
Namespace Examples.System.Net  
  
    Public Class SslTcpClient  
          
        ' The following method is invoked by the RemoteCertificateValidationDelegate.  
        Public Shared Function ValidateServerCertificate(  
            sender As Object,   
            certificate As X509Certificate,   
            chain As X509Chain,   
            sslPolicyErrors As SslPolicyErrors) As Boolean  
              
            If sslPolicyErrors = SslPolicyErrors.None Then Return True  
  
            Console.WriteLine("Certificate error: {0}", sslPolicyErrors)  
  
            ' Do not allow this client to communicate with unauthenticated servers.  
            Return False  
        End Function  
        Public Shared Sub RunClient(machineName As String, serverName As String)  
  
            ' Create a TCP/IP client socket.  
            ' machineName is the host running the server application.  
            Dim client = New TcpClient(machineName, 443)  
            Console.WriteLine("Client connected.")  
  
            ' Create an SSL stream that will close the client's stream.  
            Dim sslStream = New SslStream(  
                client.GetStream(), False,   
                New RemoteCertificateValidationCallback(AddressOf ValidateServerCertificate), Nothing)  
  
            ' The server name must match the name on the server certificate.  
            Try  
                sslStream.AuthenticateAsClient(serverName)  
            Catch e As AuthenticationException  
                Console.WriteLine("Exception: {0}", e.Message)  
  
                If e.InnerException IsNot Nothing Then  
                    Console.WriteLine("Inner exception: {0}", e.InnerException.Message)  
                End If  
  
                Console.WriteLine("Authentication failed - closing the connection.")  
                client.Close()  
                Return  
            End Try  
              
            ' Encode a test message into a byte array.  
            ' Signal the end of the message using the "<EOF>".  
            Dim messsage As Byte() = Encoding.UTF8.GetBytes("Hello from the client.<EOF>")  
              
            ' Send hello message to the server.  
            sslStream.Write(messsage)  
            sslStream.Flush()  
            ' Read message from the server.  
            Dim serverMessage = ReadMessage(sslStream)  
            Console.WriteLine("Server says: {0}", serverMessage)  
  
            ' Close the client connection  
            client.Close()  
            Console.WriteLine("Client closed.")  
        End Sub  
          
        Private Shared Function ReadMessage(sslStream As SslStream) As String  
  
            ' Read the  message sent by the server.  
            ' The end of the message is signaled using the "<EOF>" marker.  
            Dim buffer = New Byte(2048) {}  
            Dim messageData = New StringBuilder()  
            Dim bytes As Integer  
  
            Do  
                bytes = sslStream.Read(buffer, 0, buffer.Length)  
  
                ' Use Decoder class to convert from bytes to UTF8  
                ' in case a character spans two buffers.          
                Dim decoder As Decoder = Encoding.UTF8.GetDecoder()  
                Dim chars = New Char(decoder.GetCharCount(buffer, 0, bytes) - 1) {}  
                decoder.GetChars(buffer, 0, bytes, chars, 0)  
                messageData.Append(chars)  
  
                ' Check for EOF.  
                If messageData.ToString().IndexOf("<EOF>") <> -1 Then Exit Do  
                  
            Loop While bytes <> 0  
  
            Return messageData.ToString()  
  
        End Function  
  
        Private Shared Sub DisplayUsage()  
  
            Console.WriteLine("To start the client specify:")  
            Console.WriteLine("clientSync machineName [serverName]")  
            Environment.[Exit](1)  
  
        End Sub  
  
        Public Shared Function Main(args As String()) As Integer  
  
            Dim serverCertificateName As String  
            Dim machineName As String  
  
            If args Is Nothing OrElse args.Length < 1 Then  
                DisplayUsage()  
            End If  
  
            ' User can specify the machine name and server name.  
            ' Server name must match the name on the server's certificate.   
            machineName = args(0)  
  
            If args.Length < 2 Then  
                serverCertificateName = machineName  
            Else  
                serverCertificateName = args(1)  
            End If  
  
            SslTcpClient.RunClient(machineName, serverCertificateName)  
  
            Return 0  
  
        End Function  
  
    End Class  
  
End Namespace