03-22-2012 05:49 PM
Is there any way of going from a TCP connection returned from TCP Listen into a VISA Resource? I have a set of VIs that communicate over the serial port and I'd like to use them over TCP/IP but I hit a road block on the listener. If there's anyway I can create a TCP listener with VISA I'd appreciate the help. Thanks!
03-23-2012 08:01 AM
Yes, that only returns a TCP connection which is not compatible with VESA functions. You can typecast from a TCP VISA connection to a TCP connection but it doesn't look like you can do the reverse.
03-23-2012 08:32 AM
I have a bunch of VIs that communicate via a serial port and all of the serial port functions in LabVIEW are VISA functions. My VIs take a VISA resource as an input, using VISA read and write to do their operations. I can open an outbound TCP socket with VISA and uses these VIs just fine but I need to listen for an incoming TCP connection on the server-side.
So I'm looking for a way of either using VISA to listen for a TCP connection or convert the TCP connection returned by TCP Listen to a VISA resource that my VIs can use.
03-26-2012 11:29 AM
You can actually create a VISA resource for a TCP/IP device by just formatting a resource string. The necessary format can be seen in the KB How Do I Control Ethernet Instruments with NI-VISA and it sounds like you would need to use the Socket configuration unless the device supports the INSTR protocol. You can then pass that resource into standard VISA VIs like VISA open, etc.
03-26-2012 11:48 AM
Hi Milan, thanks for the reply. I have no problems creating out bound TCP connections. What I'm looking for is the ability to listen, via VESA, for an incoming connection. There doesn't appear to be any way to do this. I want to do this because I would like my VIs to be agnostic to the underlying link (serial, TCP, etc.). Otherwise, I have to have duplicated VIs for TCP and serial.
03-26-2012 12:25 PM
Looks like I created a bit of confusion here. There is no instrument or rather, I want my VI to be the "instrument". My VIs, both server and client, talk to each other. I've needed them to talk over both serial and TCP/IP. I was hoping to use VISA to make them agnostic to the underlying communications link. My first approach was to make my VIs accept VISA resources as the VISA functions work for both serial and TCP/IP. This works great except for the fact that there doesn't seem to be a way to make my VI wait for an incoming TCP connection using VESA. The only LabVIEW functions to do this are "TCP Listen" and "TCP Create Listener" but I can't go from the TCP connection ID those VIs return to a VESA resource that I can pass to my VIs to talk to each other.