"How can I tell if the destination is available before sending my MSMQ message?" #1

This is sort of defeating the main point of using MSMQ - that is, being able to send a message without worrying if the destination is available or not - but there may be a good business reason for wanting to.

Just because a machine is on-line does not mean that the MSMQ service itself is up and running. So just sending an ICMP PING to the IP address of the machine is not as helpful as you'd think.

One option is to use MSMQ's own MQPing system. As discussed here, MQPing sends a normal MSMQ message labelled "QM-Admin Commands" and there will be a corresponding message returned to the sender labelled "Ping Response". So you could send and your receive your own MQPIng message from within your application.

Here's some sample VBScript that Yoel Arnon wrote many years ago that shows the principle:

<Job ID="MQPing">

<?Job Debug="True"?>

<Reference Object="MSMQ.MSMQApplication"/>

<Script language="VBScript">

' Author: Yoel Arnon (yoel@msmq.biz)

' Date: 05-Jul-2001

' Purpose: MQping using DIRECT format name.

'          Can be used for Workgroup, cross enterprise ping, as well as regular MQPing.



Option Explicit

Dim objArgs

Set objArgs = WScript.Arguments


if (objArgs.Count = 0) Then

      WScript.Echo "Usage: MQping <MSMQ Computer to Ping> [<Timeout in seconds>]"


End If


Dim TimeOut

if (objArgs.Count > 1) Then

      TimeOut = objArgs(1) * 1000 ' Miliseconds


      TimeOut = 30000 ' 30 seconds

End If


Dim ComputerToPing

ComputerToPing = objArgs(0)



' Ping messages are sent to the target's admin queue


Dim RemoteAdminQI

Set RemoteAdminQI = WScript.CreateObject("MSMQ.MSMQQueueInfo")

RemoteAdminQI.FormatName = "DIRECT=OS:" + ComputerToPing + "private$admin_queue$"


Dim RemoteAdminQ

Set RemoteAdminQ = RemoteAdminQI.Open(MQ_SEND_ACCESS, MQ_DENY_NONE)


Dim LocalRespQI

Set LocalRespQI = WScript.CreateObject("MSMQ.MSMQQueueInfo")


LocalRespQI.PathName = ".Private$PingRespQ"


On Error Resume Next


' Delete queue if exist - may contain old response messages



On Error Goto 0




Dim WshNetwork

Set WshNetwork = WScript.CreateObject("WScript.Network")



' Build a DIRECT format name on my computer for the response queue

' Note: although the response queue already contains a format name, it may not be a DIRECT one.


LocalRespQI.formatName = "DIRECT=OS:" + WshNetwork.ComputerName + "Private$PingRespQ"


Dim LocalRespQ




' Send the Ping Message


Dim AdminMsg

Set AdminMsg = WScript.CreateObject("MSMQ.MSMQMessage")



' Ping message format:

' Label must be "QM-Admin Commands"

' Body contains "Ping=" and response string

' Ping reply will be sent to response queue


AdminMsg.Label = "QM-Admin Commands"

AdminMsg.Body = "Ping=" & ComputerToPing

AdminMsg.MaxTimeToReachQueue = TimeOut


Set AdminMsg.ResponseQueueInfo = LocalRespQI


AdminMsg.Send RemoteAdminQ



' Wait for response


Dim ReturnMsg

Set ReturnMsg = LocalRespQ.Receive(,,,TimeOut)


if ReturnMsg Is Nothing Then

      WScript.Echo "MQPing Failed"



      ' Check reply

      ' Reply begins with one NULL byte, then unicode "=" and then the response string,

      ' but no NULL terminator. We want to see if this is equal to what we sent.

      ' We have no choice but comparing the prefix (we may, for example, confuse the

      ' reply from "comp" and "comp01", but this is a risk we should take).


      Dim RespondingComputer

      RespondingComputer = MidB(ReturnMsg.Body,4) ' Excluding a leading NULL byte and Unicode "="


      ' Note - the response may contain extra characters. We should look at the prefix

      if ComputerToPing = LeftB(RespondingComputer, lenB(ComputerToPing)) Then

            WScript.Echo "MQPing Succeeded"


            WScript.Echo "Someone else answered your MQPing - Please Re-Run MQPing"

      End If

End if




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