Utilizzo di named pipe in un programma di 32-bit Visual Basic

1. Creare un token di protezione per la pipe consentire l'accesso (per rendere disponibile a qualsiasi processo un named pipe creando un token di protezione con un discrezionale elenco DACL (Access Control) contenente le voci di zero).
2. Creare named pipe.
3. Chiamare ConnectNamedPipe per bloccare fino a quando un client si connette.
4. Chiamare il metodo ReadFile e/o WriteFile per comunicare attraverso la pipe.
5. Chiamare DisconnectNamedPipe è terminato il processo tramite la pipe.
6. Entrambi CloseHandle sulla named pipe o andare al passaggio 4.

1. Chiamare CreateFile per ottenere un handle al named pipe.
2. Chiamare il metodo ReadFile e/o WriteFile per comunicare attraverso la pipe.
3. Chiamare il filehandle creato in CreateFile CloseHandle.

Named pipe server

1. Creare un nuovo progetto. In base all'impostazione predefinita, viene creato il progetto Form1.
2. Aggiungere il codice riportato di seguito al form:

      Option Explicit
      Private Const szPipeName = "\\.\pipe\bigtest"
      Private Const BUFFSIZE = 20000
      Private BigBuffer(BUFFSIZE) As Byte, pSD As Long
      Private sa As SECURITY_ATTRIBUTES
      Private hPipe As Long
   
      Private Sub Form_Click()
         Dim i As Long, dwOpenMode As Long, dwPipeMode As Long
         Dim res As Long, nCount As Long, cbnCount As Long
         For i = 0 To BUFFSIZE - 1       'Fill an array of numbers
            BigBuffer(i) = i Mod 256
         Next i
   
         'Create the NULL security token for the pipe
         pSD = GlobalAlloc(GPTR, SECURITY_DESCRIPTOR_MIN_LENGTH)
         res = InitializeSecurityDescriptor(pSD, SECURITY_DESCRIPTOR_REVISION)
         res = SetSecurityDescriptorDacl(pSD, -1, 0, 0)
         sa.nLength = LenB(sa)
         sa.lpSecurityDescriptor = pSD
         sa.bInheritHandle = True
   
         'Create the Named Pipe
         dwOpenMode = PIPE_ACCESS_DUPLEX Or FILE_FLAG_WRITE_THROUGH
         dwPipeMode = PIPE_WAIT Or PIPE_TYPE_MESSAGE Or PIPE_READMODE_MESSAGE
         hPipe = CreateNamedPipe(szPipeName, dwOpenMode, dwPipeMode, _
                                 10, 10000, 2000, 10000, sa)
   
         Do  'Wait for a connection, block until a client connects
            res = ConnectNamedPipe(hPipe, ByVal 0)
   
            'Read/Write data over the pipe
            cbnCount = 4
   
            res = ReadFile(hPipe, nCount, LenB(nCount), cbnCount, ByVal 0)
   
            If nCount <> 0 Then
   
               If nCount > BUFFSIZE Then 'Client requested nCount bytes
                  nCount = BUFFSIZE      'but only send up to 20000 bytes
               End If
               'Write the number of bytes requested
               res = WriteFile(hPipe, BigBuffer(0), nCount, cbnCount, ByVal 0)
               'Make sure the write is finished
               res = FlushFileBuffers(hPipe)
            End If
   
            'Disconnect the NamedPipe
            res = DisconnectNamedPipe(hPipe)
         Loop Until nCount = 0
   
         'Close the pipe handle
         CloseHandle hPipe
         GlobalFree (pSD)
         End
      End Sub
   					

3. Creare un nuovo modulo e aggiungere le seguenti dichiarazioni:

      Option Explicit
   
      Public Const FILE_ATTRIBUTE_NORMAL = &H80
      Public Const FILE_FLAG_NO_BUFFERING = &H20000000
      Public Const FILE_FLAG_WRITE_THROUGH = &H80000000
   
      Public Const PIPE_ACCESS_DUPLEX = &H3
      Public Const PIPE_READMODE_MESSAGE = &H2
      Public Const PIPE_TYPE_MESSAGE = &H4
      Public Const PIPE_WAIT = &H0
   
      Public Const INVALID_HANDLE_VALUE = -1
   
      Public Const SECURITY_DESCRIPTOR_MIN_LENGTH = (20)
      Public Const SECURITY_DESCRIPTOR_REVISION = (1)
   
      Type SECURITY_ATTRIBUTES
              nLength As Long
              lpSecurityDescriptor As Long
              bInheritHandle As Long
      End Type
   
      Public Const GMEM_FIXED = &H0
      Public Const GMEM_ZEROINIT = &H40
      Public Const GPTR = (GMEM_FIXED Or GMEM_ZEROINIT)
   
      Declare Function GlobalAlloc Lib "kernel32" ( _
         ByVal wFlags As Long, ByVal dwBytes As Long) As Long
      Declare Function GlobalFree Lib "kernel32" (ByVal hMem As Long) As Long
      Declare Function CreateNamedPipe Lib "kernel32" Alias _
         "CreateNamedPipeA" ( _
         ByVal lpName As String, _
         ByVal dwOpenMode As Long, _
         ByVal dwPipeMode As Long, _
         ByVal nMaxInstances As Long, _
         ByVal nOutBufferSize As Long, _
         ByVal nInBufferSize As Long, _
         ByVal nDefaultTimeOut As Long, _
         lpSecurityAttributes As Any) As Long
   
      Declare Function InitializeSecurityDescriptor Lib "advapi32.dll" ( _
         ByVal pSecurityDescriptor As Long, _
         ByVal dwRevision As Long) As Long
   
      Declare Function SetSecurityDescriptorDacl Lib "advapi32.dll" ( _
         ByVal pSecurityDescriptor As Long, _
         ByVal bDaclPresent As Long, _
         ByVal pDacl As Long, _
         ByVal bDaclDefaulted As Long) As Long
   
      Declare Function ConnectNamedPipe Lib "kernel32" ( _
         ByVal hNamedPipe As Long, _
         lpOverlapped As Any) As Long
   
      Declare Function DisconnectNamedPipe Lib "kernel32" ( _
         ByVal hNamedPipe As Long) As Long
   
      Declare Function WriteFile Lib "kernel32" ( _
         ByVal hFile As Long, _
         lpBuffer As Any, _
         ByVal nNumberOfBytesToWrite As Long, _
         lpNumberOfBytesWritten As Long, _
         lpOverlapped As Any) As Long
   
      Declare Function ReadFile Lib "kernel32" ( _
         ByVal hFile As Long, _
         lpBuffer As Any, _
         ByVal nNumberOfBytesToRead As Long, _
         lpNumberOfBytesRead As Long, _
         lpOverlapped As Any) As Long
   
      Declare Function FlushFileBuffers Lib "kernel32" ( _
         ByVal hFile As Long) As Long
   
      Declare Function CloseHandle Lib "kernel32" ( _
         ByVal hObject As Long) As Long
   					

4. Salvare il modulo.

Named pipe client

1. Creare un nuovo progetto. In base all'impostazione predefinita, viene creato il progetto Form1.
2. Aggiungere i seguenti controlli al form:

      Type             Name               Caption/Default Value
      ----             ----               ---------------------
      TextBox          cbBytes            500
      CommandButton    cmdCallNamedPipe   Call Named Pipe
      TextBox          txtReceive
   					

3. Aggiungere il codice riportato di seguito al form:

      Option Explicit
      Private Const szPipeName = "\\.\pipe\bigtest", BUFFSIZE = 20000
      Private Declare Function CallNamedPipe Lib "kernel32" Alias _
         "CallNamedPipeA" ( _
         ByVal lpNamedPipeName As String, _
         lpInBuffer As Any, _
         ByVal nInBufferSize As Long, _
         lpOutBuffer As Any, _
         ByVal nOutBufferSize As Long, _
         lpBytesRead As Long, _
         ByVal nTimeOut As Long) As Long
   
      Private Sub cmdCallNamedPipe_Click()
         Dim res As Long, myStr As String, i As Long, cbRead As Long
         Dim numBytes As Long, bArray() As Byte, temp As String
   
         numBytes = cbBytes.Text
         If cbBytes.Text < 0 Then
            MsgBox "Value must be at least 0.", vbOKOnly
            Exit Sub
         End If
         If numBytes > BUFFSIZE Then
            numBytes = BUFFSIZE
         End If
         ReDim bArray(numBytes)  'Build the return buffer
   
         'Call CallNamedPipe to do the transaction all at once
         res = CallNamedPipe(szPipeName, numBytes, LenB(numBytes), _
            bArray(0), numBytes, _
            cbRead, 30000) 'Wait up to 30 seconds for a response
   
         If res > 0 Then
            temp = Format(bArray(0), " 000")
            For i = 1 To cbRead - 1
               If (i Mod 16) = 0 Then temp = temp & vbCrLf
               temp = temp & " " & Format(bArray(i), "000")
            Next i
            txtReceive.Text = temp
         Else
            MsgBox "Error number " & Err.LastDllError & _
                   " attempting to call CallNamedPipe.", vbOKOnly
         End If
      End Sub
   
   					

4. Si noti che se il server è in esecuzione su un computer diverso da quello in cui il client è, è necessario modificare il '. ' nella variabile szPipeName al nome del computer server.
5. Salvare il modulo. Per verificare il codice sopra riportato, avviare il server e fare clic in un punto qualsiasi del form. L'applicazione server è ora il blocco e verrà visualizzato è bloccato, ma è effettivamente in attesa di al client di connettersi. Avviare l'applicazione client e scegliere "Chiamata named pipe". Il client deve inviare il valore 500 al server, che risponderà con 500 byte di dati. È possibile impostare il valore nella casella di testo cbBytes da 0 a 20000 byte. Per arrestare il server, è sufficiente inviare 0 (zero) dal client. Il client potrebbe ricevere un errore 233 (ERROR_PIPE_NOT_CONNECTED), ma questo è normale.
   
   Un altro miglioramento a quello che può includere l'utilizzo di porte di completamento I/O e/o -blocco non di letture e scritture utilizzo I/O sovrapposte. È possibile trovare ulteriori informazioni su questi argomenti in Microsoft Platform SDK.

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