vbmsgque Tutorial

INDEX

INTRODUCTION
BUILD
SERVER
CLIENT
FILTER

INTRODUCTION

vbmsgque is the VB.NET language binding of the libmsgque library.
The library was designed to simplify the client/server development using the following design rules:

1. programming language independent
2. operating system independent
3. processor hardware independent

The VB.NET language binding provide the following basic components:

• abstract class of the vbmsgque object: MqS
• interface: IServerSetup and or IServerCleanup to add server functionality
• interface: IFilterFTR and or IFilterEOF to add filter functionality
• interface: IFactory to create a new application instance
• interface: IBgError to act on asyncrone errors
• adding and removing services

BUILD

The build is different between UNIX and WINDOWS. On UNIX the automake (info automake) build environment is used and on WINDOWS the VisualExpress tools from Microsoft are used. The automake build on WINDOWS is possible but not supported.

UNIX

The example from the tutorial is using the automake build-environment from the vbmsgque tool. An example automake configuration file is available in: example/VB.NET/Makefile.am

no UNIX build possible, mono tool vbnc is still in development

WINDOWS

The VisualExpress build environment is located in the directory win.

SERVER

A vbmsgque server requires the following setup:

1. file: example/VB.NET/MyServer.vb
2. an instance of the abstract class MqS
3. the interface IServerSetup and or IServerCleanup
4. the interface IFactory to create a new application instance

The minimal server looks like:

Imports System
Imports csmsgque

Public Module example
  Private Class MyServer
    Inherits MqS
    Implements IServerSetup
    Implements IFactory

    ' service definition
    Public Function Factory() As csmsgque.MqS Implements csmsgque.IFactory.Call
      Return New MyServer()
    End Function

    ' service to serve all incomming requests for token "HLWO"
    Private Sub MyFirstService()
      SendSTART()
      SendC("Hello World")
      SendRETURN()
    End Sub

    ' define a service as link between the token "HLWO" and the callback "MyFirstService"
    Public Sub ServerSetup() Implements csmsgque.IServerSetup.Call
      ServiceCreate("HLWO", AddressOf MyFirstService)
    End Sub
  End Class

  Sub Main(ByVal args() As String)
    Dim srv As New MyServer()
    Try
      srv.ConfigSetName("MyServer")
      srv.LinkCreate(args)
      srv.ProcessEvent(MqS.WAIT.FOREVER)
    Catch ex As Exception
      srv.ErrorSet(ex)
    Finally
      srv.Exit()
    End Try
  End Sub
End Module

The server is started as network visible TCP server listen on PORT 2345 using a THREAD for every new connection request:

> mono MyServer.exe --tcp --port 2345 --thread

If you are using UNIX and if you want to setup a high-performance local server then use the build-in UDS (Unix-Domain-Sockets) capability to listen on the FILE /path/to/any/file.uds instead on a network port:

> MyServer --uds --file /path/to/any/file.uds --thread

Three things are important:

1. the send style of functions
2. the ctx.ServiceCreate(String token, AddressOf service) function
3. a connected context of type MqS

Sending data is done using a minimum of 2 steps:

1. First: start a data package with ctx.SendSTART()
2. Last: submit the a data package to the link target using one of:
   • ctx.SendEND(String token)
   • ctx.SendEND_AND_WAIT(String token, [Integer timeout])
   • ctx.SendEND_AND_CALLBACK(String token, AddressOf callback)
   • ctx.SendRETURN()

The first three SendEND... functions are used to call a remote service and the last one is used to answer an incoming service call. In-between ctx.SendSTART() and ctx.SendEND(String token) ... other SEND DATA style commands are available to fill the data package with data.

Services are created with the ctx.ServiceCreate(String token, AddressOf service) function. The first parameter is a 4 byte Token as public name. 4 byte is required because this string is mapped to a 4 byte integer for speed reason. The second parameter is an object providing the SERVICE CALLBACK interface.

The SERVICE CALLBACK function has one parameter of type MqS. This parameter refer to the original object (in our case MyServer). If the service object (in our case MyFirstService) is a subclass of the original MqS object class, the both statements SendSTART() and ctx.sendSTART() are identical.

CLIENT

A vbmsgque client requires the following setup:

1. an instance of the abstract class MqS

The minimal client looks like:

Imports System
Imports csmsgque

Public Module example
    Sub Main(ByVal args() As String)
        Dim c As New MqS()
        Try
            c.LinkCreate(args)
            c.SendSTART()
            c.sendEND_AND_WAIT("HLWO", 5)
            Console.WriteLine(c.ReadC())
        Catch ex As Exception
            c.ErrorSet(ex)
        Finally
            c.Exit()
        End Try
    End Sub
End Module

To call a network visible TCP server listen on PORT 2345 use:

> mono MyClient.exe --tcp --port 2345
> Hello World

To call a network visible UDP server listen on FILE /path/to/any/file.uds use:

> mono MyClient.exe --udp --file /path/to/any/file.uds
> Hello World

To call a local server started by the client using PIPE communication use:

> mono MyClient.exe @ mono MyServer.exe
> Hello World

FILTER

A filter has to implement the IFilterFTR or the IFilterEOF interface which requires the following functions:

• IFilterFTR, a service function to act on filter data rows. Every filter input data is a list of filter data rows and every row is a list of filter data columns. Every row is send from one filter-command to the following filter-command as FTR service request
• IFilterEOF, a service function to act on End-Of-Filter data. This service is called after the whole filter data was send. Sometimes the filter data can not be served as filter data rows (example: sorting of the input rows need to read all rows before the data can be send to the next filter command) and the EOF function is used to continue send filter data rows

The minimal filter looks like:

• filter example