TCPIP problem on 8196 PXI Controller using 2 IP addresses

[Steverhnm]

I have a PXI Chassis with an 8196 controller that is communicating to an HP server with two 1GB NICs.  Each HP NIC is configured with its own IP address and a different subnet and port#.  I have two communications paths I need (that go through a switch).

1st.  This path communicates bi-directionally every second sending data packages back and forth between server/PXI both ways.

2nd.  On occasion I need to transfer a 3 GB data file from the PXI to the Server (one-way) which will take about 2-3 minutes (I believe bandwidth limited at this point by PXI buss speed).  I am using a NI example that chunks the file sends it then re-assembles it.  Works realy slick.

Each communication path works great by itself, however, when I try to operate the two of them at the same time LabVIEW immediatley kicks the older operator off in favor of the new.  Typically I start up my two-way path then later on I will start my file transfer, then the two-way gets immediatley disconnected as soon as I open the IP address for the file transfer.

I could really use some help here, I relatively new to TCPIP communications, however, it seems pretty simple.  You open a listener and open a transmitter.  Am I trying to do something that is not possible?  Do I need to add a second network card to the PXI so I have a physically seperate NIC on the PXI or can I transmit/receive using both IPs on the same LAN connections.

Thanks !!

[ManLongAtNI]

Hello Steverh,

Can you provide more information on how you identify that the two way connection gets disconnected? I suspect you have these two sets of data transfers on seperate threads on your controller, in which case I'm curious on their priority settings if this is a RT system. It's possible the 3GB transfer takes priority and suspends the secondary transfer in which case causes the port to close on the server side.

If possible I would attach a hub to monitor the packet transfer from the controller to the switch to further investigate the behaviour when the 3GB transfer is initiated.

Let me know your thoughts. 

[Steverhnm]

Hi Glenn.

I suppose I should have said the program is in 8.6.1f1.  The program that perfroms the file transfer is dynamically loaded from the program already running the bi-directional data transfer.  I am not running RT at this time, but intend to do so in the future.  I set the priority for the file transfer VI as background(lowest).  I assume they are on seperate threads because the file transfer program is called dynamically and not loaded when the first program loads.  I'm not sure how I could otherwise control the thread its on.  I have since made inquiries to NI about the problem and they have suggested a second  physical Ethernet port, telling me that as soon as I try to open the second connection on the PXI that LV will look for an available Ethernet port and if there are no extra available then this is what happens.  That if I add the second port when I go to open the second connection it will use an available port if available.  By the way, the PXI is connected to an HP hub, but I don't have access to its information.  I have had the IT guys over and they have assured me that the pathways are open.....

I'm no LAN expert, but it seems to me that I should be able to set up a second data transfer port on the same ethernet port.  I have ordered an extra PXI card to add a second Ethernet port so we will see what happens.  I have tried every imaginable address/port combinations as well as throttling the data file transfer by splitting the file transfer into chunks.

I can see the port drop off immediatley via Task Manager LAN monitor as well as I get an error 56 when my initial bidirectional pathway comes to a screeching halt when I open the second connection.

[ManLongAtNI]

Hi Steverh,

An extra PXI card may also work. As far as communicating with your current system, can you provide more information, maybe a screenshot of the code of how we are communicating on the server side of things. Can I assume you're also using LabVIEW on the server side? What examples are you using?