C Readfile error 87 when trying to read from mailslot - c

Question

I am trying to set up a mailslot that i can write to and read from.
But when calling ReadFile to i get error 87. I have tried different approaces from MSDN and i still get error 87.
I have removed a lot of error handling in my code in order to shorten it a bit.
This are calls i do from main.
hMailslot= mailslotCreate("\\\\.\\mailslot\\myslot"); //works
hMailslot=mailslotConnect("\\\\.\\mailslot\\myslot"); //works
mailslotWrite(hMailslot,w, lstrlen(w)+1)*sizeof(CHAR); //works
mailslotRead(hMailslot); //Error 87 invalid parameter
mailslotClose(hMailslot); //?
Here is a shortened version of my code.
#define TIME_OUT MAILSLOT_WAIT_FOREVER
HANDLE mailslotCreate (char *name) {
HANDLE H = (HANDLE)CreateMailslot(name,0,TIME_OUT,(LPSECURITY_ATTRIBUTES) NULL);
return H;
}
HANDLE mailslotConnect (char * name) {
HANDLE H = CreateFile(name,GENERIC_READ|GENERIC_WRITE,FILE_SHARE_READ,0,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
return H;
}
int mailslotWrite(HANDLE mailSlot,void *msg,int msgSize) {
DWORD cbWritten;
WriteFile(mailSlot, msg, msgSize, &cbWritten, (LPOVERLAPPED) NULL);
return cbWritten;
}
int mailslotRead (HANDLE mailbox) {
DWORD cbMessage, cMessage, cbRead;
BOOL fResult;
LPTSTR Message;
fResult =GetMailslotInfo(mailbox,(LPDWORD) NULL,&cbMessage,&cMessage,(LPDWORD)NULL);
if (!fResult) //Works
{
printf("GetMailslotInfo failed with %d.\n", GetLastError());
}
Message = (LPTSTR) calloc(cbMessage,sizeof(char));
Message[0] = '\0';
fResult = ReadFile((HANDLE)mailbox,(LPVOID)Message,(DWORD)cbMessage,LPDWORD)&cbRead,(LPOVERLAPPED) NULL);
if (!fResult) //Error 87
{
printf("ReadFile failed with %d.\n", GetLastError());
free(Message);
return 0;
}
return cbRead;
}
int mailslotClose(HANDLE mailSlot){
return CloseHandle(mailSlot);
}

Answer 1

As per Microsoft, Error 87 is ERROR_INVALID_PARAMETER from ReadFile() or WriteFile()
So something is wrong with those parameters.
Also from MS: CreateMailSlot(), CreateFile() and ReadFile() definition
I've been looking at Using Mailslots and trying to compare it to what you have. About the only difference I can see is that even though they create the file with FILE_ATTRIBUTE_NORMAL, and write to it with (LPOVERLAPPED) NULL, they still supply an OVERLAPPED ov when reading the file - even though their documentation says that it is not required.
However I don't know enough to know if that is the actual issue