Using FileMapping on .NET as IPC

Download demo project - 36.6 Kb

Introduction

.NET inter-process mechanisms are very slow. With some system calls, it becomes easy to use file mapping and that's the faster mechanism for IPC.

Classes

MemMap
This class encapsulates a file mapping zone with system page-file support. All you need to do is give it a name and size.

Usage:
```
'Process 1

dim mem1 as MemMap=new MemMap("ZONE1",2048) 
mem1.writeString(0,"String to share")

'Process 2

dim mem1 as MemMap=new MemMap("ZONE1",2048) 
dim sharedString=mem1.readString(0)

mem1.close() 'at the end of both programs
```
This class handles the creation or reuse of file mapping within the "new" method and has methods for reading and writing integers and strings on a given offset.

It gives also a locking function based on InterLockedExchanged with protection against process elimination while having holding a lock.

MemChannel

This class uses the MemMap class to implement a FIFO queue of strings. You can create any number of channels by simply giving different names to each one of them.

Usage:

'Process1

dim cha1 as MemChannel=new MemChannel("CHANAME1") 
cha1.putMsg("This is the message")

'Process2

dim cha1 as MemChannel=new MemChannel("CHANAME1") 
msgbox cha1.getMsg()

cha1.close() 'at the end of both programs

EXEs

MServer.exe
Example of a server reading from a channel.
Client.exe
Example of a client writing to a channel.

Points of interest

The sample programs included here runs at 250.000 msgs per second on a PIV 3 GHz. But they block each other while accessing the channel and the CPU is not 100% busy.

With MemMap class support, it becomes easy to implement other IPC mechanisms as shared Dictionaries.

History

25-06-2005 - First version.
20-01-2007 - Second version

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with read from C++ program
ftaka

22:06 29 Apr '08

Is there a way to read from a C++ program using this? I want to get a string from a program which has written to the memory using copymemory. I've tried using this library but returns the error "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." in VB.net Help please.
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Code corrected and revised
aalday

21:18 21 Jan '07

The crash reported has ben fixed. The locking mechanism has been replaced and performance boosts to 250.000 msg/s.
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Something wrong
Alexey_i

2:33 21 Oct '06

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.OutOfMemoryException: Channel:MSERVER Buffer Full
at MClient.MemChannel.putmsgwait(String msg, Int32 timeout)
at MClient.MClient.btnSendN_Click(Object sender, EventArgs e)
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

************** Loaded Assemblies **************
mscorlib
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///d:/windows/microsoft.net/framework/v1.1.4322/mscorlib.dll
----------------------------------------
MClient
Assembly Version: 1.0.2002.24080
Win32 Version: 1.0.2002.24080
CodeBase: file:///D:/Documents%20and%20Settings/Alex/Desktop/IPC/memmap/MemMap22/MemMap/MClient/bin/MClient.exe
----------------------------------------
System.Windows.Forms
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///d:/windows/assembly/gac/system.windows.forms/1.0.5000.0__b77a5c561934e089/system.windows.forms.dll
----------------------------------------
System
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///d:/windows/assembly/gac/system/1.0.5000.0__b77a5c561934e089/system.dll
----------------------------------------
System.Drawing
Assembly Version: 1.0.5000.0
Win32 Version: 1.1.4322.573
CodeBase: file:///d:/windows/assembly/gac/system.drawing/1.0.5000.0__b03f5f7f11d50a3a/system.drawing.dll
----------------------------------------
Microsoft.VisualBasic
Assembly Version: 7.0.5000.0
Win32 Version: 7.10.3052.4
CodeBase: file:///d:/windows/assembly/gac/microsoft.visualbasic/7.0.5000.0__b03f5f7f11d50a3a/microsoft.visualbasic.dll
----------------------------------------

************** JIT Debugging **************
To enable just in time (JIT) debugging, the config file for this
application or machine (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the machine
rather than being handled by this dialog.

Re: Something wrong
aalday

21:16 21 Jan '07

The code is now corrected. The locking mechanism has been replaced and performance boosts to 250.000 msg/s. Please try again
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Faster implementation
studio_ukc

9:18 28 Sep '06

Maybe my article can help you make your code run a little faster. http://www.codeproject.com/useritems/fast_ipc.asp[^] This c++ IPC implementation does over 2,000,000 msg's per second. I was thinking about writting my own C# implementation of the IPC method I presented but time was not on my side so I never did. Any how this should give you some ideas to accelerate yours. John
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7:25 6 Nov '05

Thanks for posting such a useful module. Is it OK if I use it in my commercial application? We'll make sure your name and a link to this website is clearly listed in the code so all our developers know what a help you've been. - Brian
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Re: Copyright/Usage?
aalday

10:29 6 Nov '05

Sure, no problem
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Next time post in proper category
fwsouthern

20:51 25 Jun '05

Post in VB.NET, not C#
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Re: Next time post in proper category
aalday

22:28 25 Jun '05

OK. Changed
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FORTRAN
Anonymous

14:23 25 Jun '05

Any ideas of how this might work to do IPC with FORTRAN?
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Seems great
Daniel Turini

13:26 25 Jun '05

I didn't test it yet, but seems nice. It'd be interesting trying to write a Remoting channel over it (you just need to implement IChannel, IChannelSender and IChannelReceiver) to see if it can beat the TcpChannel. I see dead pixels Yes, even I am blogging now!
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Re: Seems great
aalday

22:40 25 Jun '05

Look for IpcChannels on .net 2.0. http://msdn2.microsoft.com/library/h9ew6576(en-us,vs.80).aspx
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