I have a Windows named pipe that I create with CreateFile (the server side was created using CreateNamedPipe). I use IO completion ports to read/write data asynchronously on both ends.
I need to send these handles to other processes after they've been opened. I tried to call CloseHandle on the handle returned from CreateIoCompletionPort, and then in the other process call CreateIoCompletionPort again. However it always fails and GetLastError returns 87 (ERROR_INVALID_PARAMETER).
I can also reproduce this in just one process, see below. Note there are no outstanding reads/write to the object before I send it.
std::wstring pipe_name = L"\\\\.\\pipe\\test.12345";
HANDLE server = CreateNamedPipeW(
pipe_name.c_str(),
PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED,
PIPE_TYPE_BYTE | PIPE_READMODE_BYTE,
1,
4096,
4096,
10000,
NULL);
SECURITY_ATTRIBUTES security_attributes = {
sizeof(SECURITY_ATTRIBUTES), NULL, TRUE};
HANDLE client = CreateFileW(
pipe_name.c_str(), GENERIC_READ | GENERIC_WRITE,
0,
&security_attributes,
OPEN_EXISTING,
SECURITY_SQOS_PRESENT | SECURITY_ANONYMOUS | FILE_FLAG_OVERLAPPED,
NULL);
ULONG_PTR key = 1;
HANDLE comp_port = CreateIoCompletionPort(client, NULL, key, 1);
BOOL b1 = CloseHandle(comp_port);
comp_port = CreateIoCompletionPort(client, NULL, key, 1);
if (comp_port == NULL) {
int last_err = GetLastError();
}
Referring to the documentation for CreateIoCompletionPort:
A handle can be associated with only one I/O completion port, and after the association is made, the handle remains associated with that I/O completion port until it [the handle] is closed.
[...] The I/O completion port handle and every file handle associated with that particular I/O completion port are known as references to the I/O completion port. The I/O completion port is released when there are no more references to it.
In other words, closing the I/O completion port handle doesn't achieve anything. The I/O completion port still exists and is permanently associated with the pipe handle. What you're attempting simply isn't possible; you will need to rearchitecture.
Note also:
It is best not to share a file handle associated with an I/O completion port by using either handle inheritance or a call to the DuplicateHandle function. Operations performed with such duplicate handles generate completion notifications. Careful consideration is advised.
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