Event log entry when service not started

[Tim_S]

I've got two LabVIEW 8.6 executables trying to talk to each other over TCP on Win7. The listening side has a service name which the other side uses. Should the listening side not be running, an entry goes into the Windows event log. I created a little LabVIEW 2011 test program that demonstrates this. Are people seeing the same behavior?

 

The event I'm getting is:

Event ID: 3299

Level: Error

Source: LabVIEW

LabVIEW information:  Error: 404 "Not Found" for "testtcpservice", file "c:/program files (x86)/national instruments/shared/ni webserver/www/testtcpservice": Can't access URL

 

Event Viewer Entries.vi

[Rolf Kalbermatter]

I've got two LabVIEW 8.6 executables trying to talk to each other over TCP on Win7. The listening side has a service name which the other side uses. Should the listening side not be running, an entry goes into the Windows event log. I created a little LabVIEW 2011 test program that demonstrates this. Are people seeing the same behavior?

 

The event I'm getting is:

Event ID: 3299

Level: Error

Source: LabVIEW

LabVIEW information:  Error: 404 "Not Found" for "testtcpservice", file "c:/program files (x86)/national instruments/shared/ni webserver/www/testtcpservice": Can't access URL

 

 

What is the problem here?

[Tim_S]

What is the problem here?

What I'm looking for is:

 

1. Is this reproducible? Do others get the same errors?

2. Is this expected (I believe so)?

 

After that, I have to decide what to do about it. My customer has discovered this, brought it up and is questioning what's wrong with the software and why is it trying to access webpages. There is actually nothing "wrong", save that the service that the software is trying to connect to isn't running and that the description of the event is misleading.

[Rolf Kalbermatter]

What I'm looking for is:

 

1. Is this reproducible? Do others get the same errors?

2. Is this expected (I believe so)?

 

After that, I have to decide what to do about it. My customer has discovered this, brought it up and is questioning what's wrong with the software and why is it trying to access webpages. There is actually nothing "wrong", save that the service that the software is trying to connect to isn't running and that the description of the event is misleading.

 

Actually it's not misleading at all. If you specify a service name rather than a port number the LabVIEW node will query the "service locator service" on the target machine to query the port number it should use. This "service locator service" is part of the NI webserver. Your target application when specyfing a service name to the Open TCP Listener will register itself with the allocated port in the local "service locator service".

 

So you have two options here:

 

1) document this behaviour in your application manual and sell it as a feature

2) Change your server application to use an explicit port when registering and your client to listen to that port

 

Note to others coming across this: In order for the service name registration to work in the LabVIEW TCP/IP nodes, one needs to make sure to have the NI System WebServer component installed on the server machine. If you build an application installer don't forget to select that component in the Additional Installs section (part of the according LabVIEW runtime engine).

[Tim_S]

OK, that's making more sense now. I had (erroneously) thought that the aliasing/lookup of the port was done more directly to the OS. I appreciate the explanation of what's going on.  

 

I think this is a feature.