how to use queues in vb.net. i want to make it like when ever i add new string into the queues, it will compare the value inside the queues first b4 add into the queues and if compare half way through, there is same value. the value will not add into the queues.
View 13 RepliesI'm trying to replicate a design pattern used in a graphical programming language called LabVIEW. One thread produces commands, and another thread, or series of threads, consumes the commands.This is very similar to using Queues in VB...but there doesn't seem to be an easy way to start the consumer thread when new items are added to the queue.
Here is what I would like to accomplish, please let me know if there is a straightforward way to accomplish this with out of box .Net functionality.1) Start the Consumer Thread...it sits idle, waiting for some new commands to appear in its Queue.2) Producer places a few commands into the Queue. Example: "Home X Axis", "Home Y Axis", "Initialize Pump", "Display Ready Message"3) Consumer thread 'wakes up' at seeing the new commands, then performs the 4 tasks specified in 2.4) Consumer thread goes 'idle' again, and simply waits for new commands to appear in the Queue.
Process can continue on and on forever. The main problem I see with Queues is that there is no 'Wait for Something to Appear in Queue then Retrieve it" functionality. I don't want to use a perpetual loop to keep checking ever n milliseconds.
I am trying to use MessageQueues to notify users of an application of data changes using the Multicast feature, but can't get it to work : the workstation that sends the message does receive it, but none of the other running workstations seem to catch the sent message.Sending messages is done as follows :
Dim sendQueue As New Messaging.MessageQueue("FormatName:MULTICAST=234.1.1.1:8001")
Dim message As New Messaging.Message("message body...")
sendQueue.Send(message)
And receiving them :
Dim receiveQueue As New Messaging.MessageQueue(".private$myQ")
receiveQueue.MulticastAddress = "234.1.1.1:8001"
receiveQueue.BeginReceive()
[code]....
So I'm obviously missing something, and I can't seem to find any good ressources on multicasting with MSMQ 3.0 in .NET.Also, what is not clear is wether I should use a local queue per workstation, or one single remote queue on a server to multicast messages ? And does using the receive method on multicast messages purge them from the queue ?On a side note, all workstations are on the same subnet, and all have MSMQ 3.0 installed.
Despite what the Queue properties dialog says, permissions are NOT totally ignored on unauthenticated queues, at least when using multicasting. If you want your queue to receive multicast messages, it must give to 'ANONYMOUS_LOGON' the right to 'Send messages'. Otherwise, multicast messages are just discarded without any notice in event logs or whatsoever (unless I missed something).
On Win7 stations (XP stations seem to do fine, which is what pointed me to the actual problem), queues created through code do not have such permissions, and hence must be manually set after creating the queue :
Dim msgQ = Messaging.MessageQueue.Create(queueName)
msgQ.SetPermissions("ANONYMOUS LOGON",
Messaging.MessageQueueAccessRights.WriteMessage)
It would seem that internally, MSMQ uses that account to write multicast messages to unauthenticated queues.
I'm using the 2.0 framework to get a list of queues from a remote machine. Sometimes the machine has a firewall and then the user has to wait 80 seconds or so before an exception is thrown stating that the machine is unavailable. Questions: Is there any way that I can set/change the timeout for GetPrivateQueues ByMachine? Is there any other method I can call before running GetPrivateQueuesByMachine to see whether the machine is responding? One that has configurable timeout, Any other solution?
View 1 RepliesI'd like to give a homework assignment to a person learning VB.NET. I'd like it to use basic inheritance and a variety of data structures including queues, lists, arrays, or stacks in a windows forms application. I was thinking of a pizza-ordering application. This would allow them to utilize some basic inheritance and practice using .NET UI elements.
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