CallNamedPipe and TransactNamedPipe don't work - c

Question

I want to send message to server and read it using named pipes. When I use WriteFile function, the message gets to the server, but TransactNamedPipe fails with error 230 (ERROR_BAD_PIPE) and CallNamedPipe fails with error 87 (INVALID_PARAMETER) or 231 (PIPE_BUSY). I've tried MSDN examples, a lot of other stuff, but still no results. Please help.
Client:
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <tchar.h>
#include <string>
#define BUFSIZE 512
int _tmain(int argc, TCHAR *argv[])
{
OVERLAPPED ov;
ZeroMemory(&ov, sizeof(OVERLAPPED));
HANDLE hPipe;
// Try to open a named pipe; wait for it, if necessary.
while (1)
{
hPipe = CreateFile(
L"\\\\.\\pipe\\PipeTest", // pipe name
GENERIC_READ | // read and write access
GENERIC_WRITE,
0, // no sharing
NULL, // default security attributes
OPEN_EXISTING, // opens existing pipe
FILE_FLAG_OVERLAPPED,
NULL); // no template file
// Break if the pipe handle is valid.
if (hPipe != INVALID_HANDLE_VALUE)
break;
DWORD lastErr = GetLastError();
// Exit if an error other than ERROR_PIPE_BUSY occurs.
if (GetLastError() != ERROR_PIPE_BUSY)
{
printf("Could not open pipe\n");
return 0;
}
// All pipe instances are busy, so wait for 2 seconds.
if (!WaitNamedPipe(L"\\\\.\\pipe\\PipeTest", 2000))
{
printf("Could not open pipe\n");
return 0;
}
}
std::wstring s;
s.resize(1024);
DWORD cbRead;
BOOL fSuccess = TransactNamedPipe(
hPipe, // pipe handle
L"Hello", // message to server
sizeof(wchar_t) * 5, // message length
&s[0],
s.size() * sizeof(wchar_t),
&cbRead, // bytes read
&ov); // not overlapped
DWORD lastErr = GetLastError();
GetOverlappedResult(hPipe, &ov, &cbRead, TRUE);
DWORD lastErr2 = GetLastError();
CloseHandle(hPipe);
return 0;
}
Server:
#include <iostream>
#include <string>
#include <Windows.h>
const std::wstring pipeName = L"\\\\.\\pipe\\PipeTest";
int main(void)
{
HANDLE hPipe;
wchar_t buffer[256];
DWORD dwRead;
OVERLAPPED ov;
ZeroMemory(&ov, sizeof(OVERLAPPED));
hPipe = CreateNamedPipe(pipeName.c_str(),
PIPE_ACCESS_DUPLEX | PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, // FILE_FLAG_FIRST_PIPE_INSTANCE is not needed but forces CreateNamedPipe(..) to fail if the pipe already exists...
PIPE_WAIT,
1,
1024 * 16,
1024 * 16,
NMPWAIT_USE_DEFAULT_WAIT,
NULL);
if (hPipe != INVALID_HANDLE_VALUE)
{
if (ConnectNamedPipe(hPipe, &ov) != FALSE) // wait for someone to connect to the pipe
{
while (ReadFile(hPipe, buffer, 255, &dwRead, &ov) != FALSE)
{
WriteFile(hPipe, L"lalala", 6 * sizeof(wchar_t), &dwRead, &ov);
DWORD lastErr1 = GetLastError();
GetOverlappedResult(hPipe, &ov, &dwRead, TRUE);
DWORD lastrr2 = GetLastError();
printf("%s", buffer);
}
}
DisconnectNamedPipe(hPipe);
}
return 0;
}

Answer 1

if you read about TransactNamedPipe
TransactNamedPipe fails if the server did not create the pipe as a
message-type pipe or if the pipe handle is not in message-read mode.
and CallNamedPipe
Calling CallNamedPipe is equivalent to calling the CreateFile (or
WaitNamedPipe, if CreateFile cannot open the pipe immediately),
TransactNamedPipe, and CloseHandle functions
so this functions work only message-type pipe
but when you create server pipe you use PIPE_TYPE_BYTE | PIPE_READMODE_BYTE
so CallNamedPipe and/or TransactNamedPipe and must fail.
you need use ReadFile/WriteFile instead. or create server with flags PIPE_TYPE_MESSAGE|PIPE_READMODE_MESSAGE and call SetNamedPipeHandleState for client handle for set it message-read mode (use PIPE_READMODE_MESSAGE)