/// <summary>
/// Set the given mailslot's read timeout.
/// </summary>
/// <param name="readTimeout">Timeout for read operations in milliseconds. Set to uint.MaxValue for infinite timeout.</param>
public static void SetMailslotTimeout(SafeMailslotHandle mailslotHandle, uint readTimeout)
{
if (!Imports.SetMailslotInfo(mailslotHandle, readTimeout))
{
throw Errors.GetIoExceptionForLastError();
}
}
/// <summary>
/// Write a message to the specified mailslot
/// </summary>
/// <param name="hMailslot">Handle to the mailslot</param>
/// <param name="lpszMessage">The message to be written to the slot</param>
static void WriteMailslot(SafeMailslotHandle hMailslot, string message)
{
int cbMessageBytes = 0; // Message size in bytes
int cbBytesWritten = 0; // Number of bytes written to the slot
byte[] bMessage = Encoding.Unicode.GetBytes(message);
cbMessageBytes = bMessage.Length;
bool succeeded = NativeMethod.WriteFile(
hMailslot, // Handle to the mailslot
bMessage, // Message to be written
cbMessageBytes, // Number of bytes to write
out cbBytesWritten, // Number of bytes written
IntPtr.Zero // Not overlapped
);
if (!succeeded || cbMessageBytes != cbBytesWritten)
{
Console.WriteLine("WriteFile failed w/err 0x{0:X}",
Marshal.GetLastWin32Error());
}
else
{
Console.WriteLine("The message \"{0}\" is written to the slot",
message);
}
}
static void Main(string[] args)
{
SafeMailslotHandle hMailslot = null;
try
{
// Try to open the mailslot with the write access.
hMailslot = NativeMethod.CreateFile(
MailslotName, // The name of the mailslot
FileDesiredAccess.GENERIC_WRITE, // Write access
FileShareMode.FILE_SHARE_READ, // Share mode
IntPtr.Zero, // Default security attributes
FileCreationDisposition.OPEN_EXISTING, // Opens existing mailslot
0, // No other attributes set
IntPtr.Zero // No template file
);
if (hMailslot.IsInvalid)
{
throw new Win32Exception();
}
Console.WriteLine("The mailslot ({0}) is opened.", MailslotName);
// Write messages to the mailslot.
// Append '\0' at the end of each message considering the native C++
// Mailslot server (CppMailslotServer).
WriteMailslot(hMailslot, "Message 1 for mailslot\0");
WriteMailslot(hMailslot, "Message 2 for mailslot\0");
Thread.Sleep(3000); // Sleep for 3 seconds for the demo purpose
WriteMailslot(hMailslot, "Message 3 for mailslot\0");
}
catch (Win32Exception ex)
{
Console.WriteLine("The client throws the error: {0}", ex.Message);
}
finally
{
if (hMailslot != null)
{
hMailslot.Close();
hMailslot = null;
}
}
}
/// <summary>
/// Get information for the given mailslot.
/// </summary>
public static MailslotInfo GetMailslotInfo(SafeMailslotHandle mailslotHandle)
{
MailslotInfo info = new MailslotInfo();
unsafe
{
if (!Imports.GetMailslotInfo(
hMailslot: mailslotHandle,
lpMaxMessageSize: &info.MaxMessageSize,
lpNextSize: &info.NextSize,
lpMessageCount: &info.MessageCount,
lpReadTimeout: &info.ReadTimeout))
{
throw Errors.GetIoExceptionForLastError();
}
}
return(info);
}
public static extern bool ReadFile(SafeMailslotHandle handle,
byte[] bytes, int numBytesToRead, out int numBytesRead,
IntPtr overlapped);
public static extern bool WriteFile(SafeMailslotHandle handle,
byte[] bytes, int numBytesToWrite, out int numBytesWritten,
IntPtr overlapped);
public static extern bool WriteFile(SafeMailslotHandle handle,
byte[] bytes, int numBytesToWrite, out int numBytesWritten,
IntPtr overlapped);
public static extern bool GetMailslotInfo(SafeMailslotHandle hMailslot,
IntPtr lpMaxMessageSize,
out int lpNextSize, out int lpMessageCount,
IntPtr lpReadTimeout);
public static extern bool GetMailslotInfo(SafeMailslotHandle hMailslot,
IntPtr lpMaxMessageSize,
out int lpNextSize, out int lpMessageCount,
IntPtr lpReadTimeout);
public static extern bool ReadFile(SafeMailslotHandle handle,
byte[] bytes, int numBytesToRead, out int numBytesRead,
IntPtr overlapped);
/// <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(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 = NativeMethod.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 == 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 = NativeMethod.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 = NativeMethod.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);
}
static void Main(string[] args)
{
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.
SECURITY_ATTRIBUTES sa = null;
sa = CreateMailslotSecurity();
// Create the mailslot.
hMailslot = NativeMethod.CreateMailslot(
MailslotName, // The name of the mailslot
0, // No maximum message size
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>
/// Write a message to the specified mailslot
/// </summary>
/// <param name="hMailslot">Handle to the mailslot</param>
/// <param name="lpszMessage">The message to be written to the slot</param>
static void WriteMailslot(SafeMailslotHandle hMailslot, string message)
{
int cbMessageBytes = 0; // Message size in bytes
int cbBytesWritten = 0; // Number of bytes written to the slot
byte[] bMessage = Encoding.Unicode.GetBytes(message);
cbMessageBytes = bMessage.Length;
bool succeeded = NativeMethod.WriteFile(
hMailslot, // Handle to the mailslot
bMessage, // Message to be written
cbMessageBytes, // Number of bytes to write
out cbBytesWritten, // Number of bytes written
IntPtr.Zero // Not overlapped
);
if (!succeeded || cbMessageBytes != cbBytesWritten)
{
Console.WriteLine("WriteFile failed w/err 0x{0:X}",
Marshal.GetLastWin32Error());
}
else
{
Console.WriteLine("The message \"{0}\" is written to the slot",
message);
}
}
public unsafe static extern bool SetMailslotInfo(
SafeMailslotHandle hMailslot,
uint lReadTimeout);
public unsafe static extern bool GetMailslotInfo(
SafeMailslotHandle hMailslot,
uint *lpMaxMessageSize,
uint *lpNextSize,
uint *lpMessageCount,
uint *lpReadTimeout);
public static extern bool SetMailslotInfo([In] SafeMailslotHandle hMailslot, uint lReadTimeout);
/// <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(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 = NativeMethod.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 == 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 = NativeMethod.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 = NativeMethod.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;
}
