static void Main(string[] args)
{
NativeMethods.SafeMailslotHandle hMailslot = null;
try
{
// Prepare the security attributes (the lpSecurityAttributes parameter
// in CreateMailslot) for the mailslot. This is optional. If the
// lpSecurityAttributes parameter of CreateMailslot is NULL, the
// mailslot gets a default security descriptor and the handle cannot
// be inherited. The ACLs in the default security descriptor of a
// mailslot grant full control to the LocalSystem account, (elevated)
// administrators, and the creator owner. They also give only read
// access to members of the Everyone group and the anonymous account.
// However, if you want to customize the security permission of the
// mailslot, (e.g. to allow Authenticated Users to read from and
// write to the mailslot), you need to create a SECURITY_ATTRIBUTES
// structure.
NativeMethods.SECURITY_ATTRIBUTES sa = null;
sa = CreateMailslotSecurity();
// Create the mailslot.
hMailslot = NativeMethods.CreateMailslot(
MailslotName, // The name of the mailslot
0, // No maximum message size
NativeMethods.MAILSLOT_WAIT_FOREVER, // Waits forever for a message
sa // Mailslot security attributes
);
if (hMailslot.IsInvalid)
{
throw new Win32Exception();
}
Console.WriteLine("The mailslot ({0}) is created.", MailslotName);
// Check messages in the mailslot.
Console.Write("Press ENTER to check new messages or press Q to quit ...");
string cmd = Console.ReadLine();
while (!cmd.Equals("Q", StringComparison.OrdinalIgnoreCase))
{
Console.WriteLine("Checking new messages...");
ReadMailslot(hMailslot);
Console.Write("Press ENTER to check new messages or press Q to quit ...");
cmd = Console.ReadLine();
}
}
catch (Win32Exception ex)
{
Console.WriteLine("The server throws the error: {0}", ex.Message);
}
finally
{
if (hMailslot != null)
{
hMailslot.Close();
hMailslot = null;
}
}
}
/// <summary>
/// Read the messages from a mailslot by using the mailslot handle in a call
/// to the ReadFile function.
/// </summary>
/// <param name="hMailslot">The handle of the mailslot</param>
/// <returns>
/// If the function succeeds, the return value is true.
/// </returns>
static bool ReadMailslot(NativeMethods.SafeMailslotHandle hMailslot)
{
int cbMessageBytes = 0; // Size of the message in bytes
int cbBytesRead = 0; // Number of bytes read from the mailslot
int cMessages = 0; // Number of messages in the slot
int nMessageId = 0; // Message ID
bool succeeded = false;
// Check for the number of messages in the mailslot.
succeeded = NativeMethods.GetMailslotInfo(
hMailslot, // Handle of the mailslot
IntPtr.Zero, // No maximum message size
out cbMessageBytes, // Size of next message
out cMessages, // Number of messages
IntPtr.Zero // No read time-out
);
if (!succeeded)
{
Console.WriteLine("GetMailslotInfo failed w/err 0x{0:X}",
Marshal.GetLastWin32Error());
return(succeeded);
}
if (cbMessageBytes == NativeMethods.MAILSLOT_NO_MESSAGE)
{
// There are no new messages in the mailslot at present
Console.WriteLine("No new messages.");
return(succeeded);
}
// Retrieve the messages one by one from the mailslot.
while (cMessages != 0)
{
nMessageId++;
// Declare a byte array to fetch the data
byte[] bBuffer = new byte[cbMessageBytes];
succeeded = NativeMethods.ReadFile(
hMailslot, // Handle of mailslot
bBuffer, // Buffer to receive data
cbMessageBytes, // Size of buffer in bytes
out cbBytesRead, // Number of bytes read from mailslot
IntPtr.Zero // Not overlapped I/O
);
if (!succeeded)
{
Console.WriteLine("ReadFile failed w/err 0x{0:X}",
Marshal.GetLastWin32Error());
break;
}
// Display the message.
Console.WriteLine("Message #{0}: {1}", nMessageId,
Encoding.Unicode.GetString(bBuffer));
// Get the current number of un-read messages in the slot. The number
// may not equal the initial message number because new messages may
// arrive while we are reading the items in the slot.
succeeded = NativeMethods.GetMailslotInfo(
hMailslot, // Handle of the mailslot
IntPtr.Zero, // No maximum message size
out cbMessageBytes, // Size of next message
out cMessages, // Number of messages
IntPtr.Zero // No read time-out
);
if (!succeeded)
{
Console.WriteLine("GetMailslotInfo failed w/err 0x{0:X}",
Marshal.GetLastWin32Error());
break;
}
}
return(succeeded);
}
