Operating System - OpenVMS

Two network Cards vs Application

Occasional Contributor

Two network Cards vs Application

Hi all,

I have an application written in C language using socket routines to communicate with a machine. This application has been running for years with no problem detected.

Last week our IT team put another network card in VMS machine and the communication became too instable, sometimes works, sometimes doesn't.

Does anyone have an idea about what's happening?

OpenVMS AXP 7.3-2
TCPIP Services 5.4
Honored Contributor

Re: Two network Cards vs Application

Yeah, you need to do some debugging and figure out if this is the network card, a network issue, a duplex or speed setting or negotiation issue, an IT-induced problem, a VMS bug or (best guess) your code is buggy.

That you're here implies that latent errors often implies that the application code is the likely culprit.

You'll next and justifiably point out that the code has run flawlessly for [insert years], which is typical of the story arc of previous posters with buggy code.

We'll then ask for a reproducer of the issue, and you'll eventually be convinced that's necessary, but will have some difficulty creating that reproducer, as it's probably something in the existing application code; the standalone reproducers will tend to work.

Which then leads to a discussion of asynchronous synchronization techniques, proper IOSB handling and allocations, and various related issues.

If the story arc here ends where it often does, the C code is found to have one or more latent errors in a central I/O path, and which have been exacerbated by performance differences with the controller.

For the occasional variation to maintain interest in the usual "it broke! why?" story arc here, sometimes we'll work through this with you to discover that there's a bad or loose cable, or a faulty controller, or a switch is set incorrectly or has mis-negotiated its speed setting or its duplex setting, an IP or VMS software bug that's come to the fore, or the switch port has gone weird as managed switches are occasionally wont to do.
Frequent Advisor

Re: Two network Cards vs Application

to isolate the problem you can use tcptrace and tcpdump utilities.

It is possible that application does not know which IP interface (network card) to use to communicate with that machine.
Andy Bustamante
Honored Contributor

Re: Two network Cards vs Application

Please provide the address and mask for each interface. Also list the default route and any other routes listed.

If you don't have time to do it right, when will you have time to do it over? Reach me at first_name + "." + last_name at sysmanager net