[VB6] PipeRPC - RPC Over Named Pipes

[dilettante]

Title

PipeRPC, a UserControl providing remote procedure calls over Named Pipes written in VB6.

Description

PipeRPC is a VB6 UserControl that uses Named Pipes to provide a very easy to use mechanism to make calls between clients and servers running (a.) in the same machine or (b.) across a Local Area Network.

No more fighting with the Winsock control.

No more struggling with DCOM (PipeRPC is great for portable applications that use reg-free COM).

None of the ugliness of Web Services.

Feature list

• Client and server functionality in one control.
• Clients can make connected or disconnected (one time) calls.
• Uses Named Pipes, so no firewall rules are required.
• Works whether your LAN is based on TCP/IP, NetBEUI, or IPX/SPX network protocols. No TCP/IP required!
• So easy.... well anyone can do it.

Screenshot

N/A since this is not a visible control at runtime.

Author name

Bob Riemersma

System requirements

Requires Windows 2000 or later.

For machine-to-machine operation:

Windows Networking enabled, firewalls must permit Windows Networking traffic ("File and Print Sharing").

A common Workgroup or Domain and common Users. The Windows Client and Server services must be running.

No special processor, disk, or memory requirements. Requires Visual Basic 6.0 development system, preferably Service Pack 6b or later, Standard Edition or better.

License info

Copyright © 2011 Robert D. Riemersma, Jr.
All Rights Reserved

PipeRPC is free for general use for any legal purpose, and derivative works are encouraged. Users are responsible for determining fitness and proper use. No liability is accepted and no warranty or guarantee of support is offered. This is “as is” software and related documentation and examples.

PipeRPC and related materials may be freely distributed in source or binary form as long as the notices are kept intact. Programs using PipeRPC do not require attribution in documentation or at runtime, however there is a Copyright property programs could use to display such information in About dialogs, etc. if desired.

Usage

Add the UserControl to your VB6 project. PipeRPC.rtf contains developer documentation, sample projects are also included in the package.

A Minimal Client and Server

Here is a "calculation client" that passes two operands and an operator to the server and displays the returned result:

Option Explicit

Private Request() As Byte
Private Response() As Byte
Private Operation As String

Private Sub cmdCalculate_Click()
    Request = txtA.Text & "|" _
            & Operation & "|" _
            & txtB.Text
    ReDim Response(199)
    pipeCalculate.PipeCall Request, Response
    txtResults.Text = Response
    txtA.SetFocus
End Sub

Private Sub Form_Load()
    Operation = "+"
End Sub

Private Sub optOperation_Click(Index As Integer)
    Operation = Choose(Index + 1, "+", "-", "*", "÷")
End Sub

Here is the calculation server:

Option Explicit

Private Sub Form_Load()
    pipeCalculate.Listen
End Sub

Private Sub Form_Unload(Cancel As Integer)
    pipeCalculate.ClosePipe
End Sub

Private Sub pipeCalculate_Called(ByVal Pipe As Long, Request() As Byte, Response() As Byte)
    Dim ReqParts() As String
    
    ReqParts = Split(Request, "|")
    On Error Resume Next
    Select Case ReqParts(1)
        Case "+"
            Response = CStr(CDbl(ReqParts(0)) + CDbl(ReqParts(2)))
        Case "-"
            Response = CStr(CDbl(ReqParts(0)) - CDbl(ReqParts(2)))
        Case "*"
            Response = CStr(CDbl(ReqParts(0)) * CDbl(ReqParts(2)))
        Case "÷"
            Response = CStr(CDbl(ReqParts(0)) / CDbl(ReqParts(2)))
    End Select
    If Err Then Response = Err.Description
End Sub

[dilettante]

To clarify the sample code above, several properties such as the PipeName were set via the IDE Properties panel. A working version is included in the attachment above as Demo 2.

[akhileshbc]

Hi dilettante

Do you have the VB.Net equivalent ?

I'm in need of implementing a communication channel between applications which are connected in a LAN. What I have in mind is to use TCP class to create the client and listener, and do the communication. But is there a way to use Named Pipes ?

Thanks

[dilettante]

I believe that in .Net they work hard to hide Named Pipes from programmers. While you can use Named Pipes via WCF within a machine I'm pretty sure they don't allow it across a LAN (for "security reasons" they say).

So you'd have to resort to PInvoke and API calls.

TCP/IP works fine, it is just slower within a machine and requires firewall rules and stealing/reserving port numbers between and among machines. A lot of people just "Trust The Force" and pick a port number hoping it doesn't collide with another service.

But you ought to be able to use WCF with TCP between machines, saving you a lot of hand coding working with the Client and Listener.

[akhileshbc]

Thanks for the info

[dilettante]

You might look at this:

http://blogs.msdn.com/b/bclteam/arch...an-patten.aspx

[akhileshbc]

You might look at this:

http://blogs.msdn.com/b/bclteam/arch...an-patten.aspx

Thanks

I found a code sample in here. The author had referenced that blog you have posted too.

[dilettante]

Small corrections to just the documentation.

[Arag]

Hey dilettante!!!
That's just amazing! Thanks a lot man!!! You helped me a lot!
Happy codings!

[fidnah]

hi
thanks for this article
when i run this program there is an error: pipe#0 system error 231
can you help me?i m realy need to it.
thanks

[dilettante]

This is:

ERROR_PIPE_BUSY (231) All pipe instances are busy.

See System Error Codes.

Do you have more than 1 client? The PipeRPC control defaults to MaxClients = 1. You can change this a design time or run time before calling the Listen method.

From the documentation provided:

MaxClients Property

This property can only be set while PipeRPC is not listening.

MaxClients As Integer

This value can be from 1 to 255 (where 255 means “unlimited”). In many cases you will have just one client, so the default value is 1. PipeRPC makes every attempt to keep unused slots closed to help reduce the memory impact of pipe instances.

[Black_Storm]

hi i need to get output from ipc pipe.i have a software document with these contents :

.
.
.
Unfortunately, it's not as easy to test the IPC protocol on Windows, since Windows ports of socat (in
Cygwin and MSYS2) don't understand named pipes. In the absence of a simple tool to send and receive
from bidirectional pipes, the echo command can be used to send commands, but not receive replies from
the command prompt.

You can send commands from a command prompt :

echo commands >\\.\pipe\mypipename

To be able to simultaneously read and write from the IPC pipe, like on Linux, it's necessary to write an
external program that uses overlapped file I/O (or some wrapper like .NET's NamedPipeClientStream.)

You can open the pipe in PuTTY as "serial" device. This is not very comfortable, but gives a way to test
interactively without having to write code

and NamedPipeClientStream sample is :

using System;
using System.IO;
using System.IO.Pipes;

class PipeClient
{
    static void Main(string[] args)
    {
        using (NamedPipeClientStream pipeClient =
            new NamedPipeClientStream(".", "testpipe", PipeDirection.In))
        {

            // Connect to the pipe or wait until the pipe is available.
            Console.Write("Attempting to connect to pipe...");
            pipeClient.Connect();

            Console.WriteLine("Connected to pipe.");
            Console.WriteLine("There are currently {0} pipe server instances open.",
               pipeClient.NumberOfServerInstances);
            using (StreamReader sr = new StreamReader(pipeClient))
            {
                // Display the read text to the console
                string temp;
                while ((temp = sr.ReadLine()) != null)
                {
                    Console.WriteLine("Received from server: {0}", temp);
                }
            }
        }
        Console.Write("Press Enter to continue...");
        Console.ReadLine();
    }
}

Unfortunately, although I tested many examples in the forum, I still could not get the output from

echo commands >\\.\pipe\mypipename

for example this command in linux :

echo '{ "command": ["aa", "bb"] }' | socat - /mypipename

get result :

{"data":xxxxxx,"error":"success"}

but with convert to pipe in widnows :

echo { "command": ["aa", "bb"] } >\\.\pipe\mypipename

return hidden data like as empty the only way need connect to that \\.\pipe\mypipename and stream output data

I also tested your attachment and it did not work, how could I get the output?

[MountainMan]

dilettante,

I am thinking of converting your control for use in 64-bit VBA. Since it is almost impossible to write a control for 64-bit VBA in VB6/VBA, I thought of converting it to a class module. Before I start, I have 2 questions for you: a) was there a specific reason you wrote this a control instead of a class module (especially since it has no visible component) and b) is there anything you are aware of that would make this conversion impossible? Thanks.

MountainMan

[dilettante]

Most likely in order to host a Timer control.

This was used to poll for new input because we can't just hang on synchronous reads and overlapped I/O is clumsy to accomplish in VB6.

[dilettante]

I also tested your attachment and it did not work, how could I get the output?

This is built around CallNamedPipeW. it sounds like you want to do stream I/O instead.

[soorya]

Hi,
I was looking something similar for my VB6 need and finally landed on this wonderful post.

I have some doubt about NamedPipe concept in Windows.
Can you please clear me ?

1) To test this PipeRPC Named Pipe, should we need another Windows system on LAN or on Internet ?
Or we can very well do this on single PC itself between 2 applications ?

2) I do lot of Client/Server logical applications on the same PC because VB6 exe can work only with 2 GB memory limit (4GB after patching). We need to play many graphics and videos on VB6 application, which is not possible on single VB6 exe. So we run each videos on each exe and IPC via Winsock/SendMessage API.
Can we use PipeRPC Named Pipe to deal this on single PC ?

3) I badly need of this PipeRPC Named Pipe to access ffmpeg video stream inside VB6 application. ffmpeg seems support Named Pipe File. I will write video stream on the named pipe file via ffmpeg and play that from inside VB6 app.
As Windows doesn't support mkfifo to write fifo file, I may use this instead.
I should be a wonderful use case.
Can I use on single PC itself ?

If so how to deal with the path : "\\<server>\pipe\” or "\\.\pipe\LOCAL" on single PC ?

Can you please guide me how to use it with ffmpeg ?

NOTE:
Kindly make better sample VB6 application to understand this concept better.
Your sample code shows nothing.
Usually some Hello World messaging could be seen to test RPC/IPC
Which is missing.

Thanks in advance