Creating Unidirectional Message-based Named Pipe

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Date: Mon, 20 Sep 2004 13:40:49 -0700

I am writing two services in VB.NET, one of which needs to send text strings
to the other. After reading, I
decided (perhaps incorrectly) that named pipes would be the best
interprocess communication method
for this task.

I set about creating, on the pipe's server side, a new thread which would
instantiate a blocking inbound message pipe, and the
client side which would write to that pipe when needed. Being on the same
PC, security is not an issue (I think).

I first tried MS example from the KB article
(http://support.microsoft.com/?kbid=871044) plugged into my
services at the appropriate locations (threads and all) and it works as
advertised. The only problem there
is that this is a bidirectional pipe that transports an integer and a byte
array.

I have spent a few days trying to change the code. The latest simple attempt
is to change the pipe type to INBOUND.
When I do so, I get an error 5 (Invalid procedure call) on the client side.
(short PIPE_ACCESS_INBOUND=&H1s)

I have tried changing the declaration of the sample to a string or 1
dimensional Byte array (rather than an Integer) and get an
error 1214 (type mismatch) in the Error object's LastDLLError. According to
my Win32 API book (Appleman) this declaration is type ANY,
so I should be able to change the type, as long as they match on both ends
of the pipe, right?

SERVER SIDE DECLARATION (from the KB article):
Declare Function CreateNamedPipe Lib "kernel32" Alias "CreateNamedPipeA" _
(ByVal lpName As String, ByVal dwOpenMode As Integer, _
ByVal dwPipeMode As Integer, ByVal nMaxInstances As Integer, _
ByVal nOutBufferSize As Integer, ByVal nInBufferSize As Integer, _
ByVal nDefaultTimeOut As Integer, ByVal lpSecurityAttributes As IntPtr _
) As Integer

Declare Function ConnectNamedPipe Lib "kernel32" _
    (ByVal hNamedPipe As Integer, ByVal lpOverlapped As Integer) As Integer

Declare Function ReadFile Lib "kernel32" _
(ByVal hFile As Integer, ByRef lpBuffer As INTEGER,
_<<<<---------------------change here
ByVal nNumberOfBytesToRead As Integer, ByRef lpNumberOfBytesRead As Integer,
_
ByVal lpOverlapped As Integer _
) As Integer

CLIENT SIDE MATCHING DECLARATION:
Public Declare Function CallNamedPipe Lib "kernel32" Alias "CallNamedPipeA"
_
(ByVal lpNamedPipeName As String, _
ByRef lpInBuffer As INTEGER,
_<<<<--------------------------------------------change here
ByVal nInBufferSize As Integer, _
ByRef lpOutBuffer As Byte, _
ByVal nOutBufferSize As Integer, _
ByRef lpBytesRead As Integer, ByVal nTimeOut As Integer) As Integer

1) Does anyone have example code for such a pipe? (client to server
communication, message-type, text messages)
2) Does anyone have any idea why changing the declared type from integer to
anything else causes such problems?
3) Is there a good way to debug these problems with API calls?

Sorry if I'm missing something obvious, I've only started switching to .NET
for 3 weeks now...Please be gentle!
Thanks!
FB

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