What I do:
- I'm beginning a transaction and set the dataset in edit mode
- I get a proper PathName() for a BLOB FILESTREAM column (I've created a
view for that table with PathName() column)
- I read a transaction token (varbinary data - array of byte) and the value
looks correct.
- I call imported OpenSQLFilestream function to get handle with read/write
mode. LastError (6) measn INVALID FILE HANDLE, and the value is AFAIR
0xFFFFFFFF.

Most examples I saw do the same (although they're in a managed code C# or
VB.NET but they import the same Win32 OpenSQLFilestream function). Do you
have any idea why I cannot get a valid file handle?

type
  TtxnToken = array of byte;

Some consts I use:
<code>
const
  SQL_FILESTREAM_READ        = 0;
  SQL_FILESTREAM_WRITE       = 1;
  SQL_FILESTREAM_READWRITE   = 2;

  SQL_FILESTREAM_OPEN_NONE                  = $00000000;
  SQL_FILESTREAM_OPEN_FLAG_ASYNC            = $00000001;
  SQL_FILESTREAM_OPEN_FLAG_NO_BUFFERING     = $00000002;
  SQL_FILESTREAM_OPEN_FLAG_NO_WRITE_THROUGH = $00000004;
  SQL_FILESTREAM_OPEN_FLAG_SEQUENTIAL_SCAN  = $00000008;
  SQL_FILESTREAM_OPEN_FLAG_RANDOM_ACCESS    = $00000010;
</code>
My BLOB reading proc:

<code>
procedure TSQLFileStream.ReadFromSQL(AStream: TStream);

const
  BufferSize = 8192;

var
  Buffer: PChar;
  ReadBytes: Cardinal;
  TokenField: TVarBytesField; // a field with array of byte value
  FHandle: THandle;
  er: Cardinal;

begin
  // Start a transaction
  FQuery.Connection.StartTransaction;

  // Get a transaction token
  FTokenQuery.Open('SELECT GET_FILESTREAM_TRANSACTION_CONTEXT() as Token');
  TokenField := TVarBytesField(FTokenQuery.FieldByName('Token'));

  // Get a file handle
  FHandle := OpenSqlFilestream(
    PChar(FSQLFilePath),
    SQL_FILESTREAM_READ,
    SQL_FILESTREAM_OPEN_NONE,
    TokenField.Value,
    TokenField.Size,
    nil);
  FTokenQuery.Close;

  if (FHandle <> 0) and (FHandle <> $FFFFFFFF) then
  // Valid handle
  begin
    // Prepare buffer
    GetMem(Buffer, BufferSize);
    try
      // Read the file while no error and ReadBytes > 0, ReadBytes is
evaluated after reading
      while Windows.ReadFile(FHandle, Buffer^, BufferSize, ReadBytes, nil)
and (ReadBytes > 0) do
        AStream.Write(Buffer^, ReadBytes)
    finally
      // Free buffer memory
      FreeMem(Buffer);
    end;
    // Close file handle
    CloseHandle(FHandle);
  end else
  begin
    er := GetLastError;
    MessageBox(0, PChar('Error ' + IntToStr(er)), 'End', 0);
  end;
  // End the transaction
  FQuery.Connection.Commit;
end;
</code>

   If the function succeeds, the return value is an open handle to a
   specified file. If the function fails, the return value is
   INVALID_HANDLE_VALUE. For extended error information, call
   GetLastError().

So I would suggest that you add a call to GetLastError() to get better
information.

I would also suggest that you verify that PChar(FSQLFilePath) gives you
a pointer to a Unicode value.

--
Erland Sommarskog, SQL Server MVP, esq...@sommarskog.se

if (FHandle <> 0) and (FHandle <> $FFFFFFFF) then
  // Valid handle
  begin
        // here some routines
  end else
  begin
    er := GetLastError;
    MessageBox(0, PChar('Error ' + IntToStr(er)), 'End', 0);
  end;

CREATE TABLE [dbo].[FSBLOBs](
  [BLOBID] int IDENTITY(1,1) NOT NULL Primary Key,
  [BLOBName] varchar(50) NULL,
  [BLOBData] varbinary(max) filestream NULL,
  [BLOBPath] varchar(max) NULL,
  [rowguid] uniqueidentifier NOT NULL rowguidcol unique
)

CREATE TRIGGER [dbo].[T_FSBLOBS_IU] ON [dbo].[FSBLOBs]
AFTER INSERT,UPDATE
AS
BEGIN
  SET NOCOUNT ON;
  if UPDATE([BLOBData])
     UPDATE [dbo].[FSBLOBs]
     SET [BLOBPath] = CONVERT(varchar(max), i.[BLOBData].PathName())
         FROM [FSBLOBs] AS fs
             INNER JOIN INSERTED AS i
             ON fs.[BLOBID] = i.[BLOBID]
   SET NOCOUNT OFF;
END

I fill the path in a table trigger and it's not a Unicode data. Thank you
for the tip.

Eh, wait a minute. I looked your code last night about the last thing I
did. I might have been a little tired... I can't see that you set
FSQLFilePath anywhere. You should get the value with the PathName
function from SQL. That part seems to be missing. (Disclaimer: I'm at
work now, and I don't have the time look in the SQL 2008 docs, so I talk
from memory.(

--
Erland Sommarskog, SQL Server MVP, esq...@sommarskog.se

You would think that not having the port open would produce a different
error message though.

Cheers,
Bob Beauchemin
SQLskills

I would suggest that you try to retrieve the path at run-time.

--
Erland Sommarskog, SQL Server MVP, esq...@sommarskog.se

Also, did you store any values before you made the configuration changes?

One operation that definitely can change the path is if you backup
the database and restore it elsewhere.

--
Erland Sommarskog, SQL Server MVP, esq...@sommarskog.se

I've installed Visual Studio 2008 Express on my (developer) machine to test
if it's a problem in my library it but unfortunatelly it cannot connect
remote database - only local connections :(