System Coupling hostname issue in ANSYS 2023R1 and 2023R2

- August 21, 2023 at 7:02 pm
  The Dr. Sky
  Subscriber
  I'm running a 2-way FSI problem consisting of the transient flow in a carotid bifurcation geometry. I'm using CFX as the flow solver. The simulations run on a local workstation accessing the Ansys license on a remote license server.
  I can confirm that my setup is correct and that the license server can be accessed since my simulations run flawlessly in ANSYS 2022R2 using System Coupling in workbench or the System Coupling GUI outside workbench. My issues started with 2023R1. After creating the same exact setup, System Coupling is unable to connect the participants and exits with the folowing error message:
  waiting connections from coupling participants...
  +-----------------------------------------------------------------------------+
  | "System coupling solution stopped before all participants connected. A |
  | solver failure occurred during the run in the Fluid Flow (CFX) system" |
  +-----------------------------------------------------------------------------+
  Traceback (most recent call last):
  File "PyLib\cosimulation\solver\__init__.py", line 149, in solve
  File "PyLib\kernel\util\Memory.py", line 208, in wrapper
  File "PyLib\cosimulation\solver\__init__.py", line 541, in __startParticipantsControlled
  File "PyLib\cosimulation\participantmanager\participantManager.py", line 401, in startParticipants
  cosimulation.solver.CosimulationError.CosimulationError: "System coupling solution stopped before all participants connected. A solver failure occurred during the run in the Fluid Flow (CFX) system"
  Looking at the CFX log, the inability to connect all participants seems to be related to the following issue:
  " ERROR #001100279 has occurred in subroutine ErrAction. |
  | Message: |
  | ANSYS CFX is unable to connect to the system coupling service on |
  | DESKTOP-IFHHT69.Kennesaw.EDU through port 51268. Please ensure th- |
  | at the host name and the port number are correct."
  There seems to be a mismatch between the hostname used by System Coupling (i.e., DESKTOP-IFHHT69.Kennesaw.EDU) and the hostname used by CFX (i.e., DESKTOP-IFHHT6). The correct hostname is the one reported by CFX. The domain added by System Coupling (.Kennesaw.EDU) should not be part of the hostname.
  With the release of 2023R2, I was hoping that this issue would disappear. Unfortunately, after installing 2023R2 today and setting up the same model again, I still obtain the same error message. As a result, I removed 2023R2 and reinstalled 2022R2. I can confirm that the simulations work with no error message and that system coupling is able to connect all participants in this older release. I can also confirm that, with this older release, the correct hostname (DESKTOP-IFHHT6) is used by both CFX and System Coupling.
  1. Why are both 2023 releases unable to run a model that was successful in 2022R2? Any troubleshooting suggestions are welcome.
  2. If the issue is truly related to the fact that System Coupling, for some reason, uses an incorrect hostname, how can I manually input the correct hostname in System Coupling prior to running a simulation? Running the System Coupling GUI outside workbench did not resolve the issue.
- August 22, 2023 at 4:14 pm
  
  MangeshANSYS
  Ansys Employee
  
  Hello,
  Please refer to Participant connection issues section at
  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v232/en/sysc_ug/kil_participants.html
  that includes what may cause this andhow to resolve.
  Hope this is helpful
  - August 22, 2023 at 4:32 pm
    
    The Dr. Sky
    Subscriber
    
    Thank you for providing this link. I followed the recommendations listed under "Participant connection issues". The host file located in C:\Windows\System32\Drivers\etc is the default host file and has not been edited. I don't this could have been the issue given that the same simulations on the same machine run succcessfully on 2022R2. Any other recommendation?
- August 25, 2023 at 12:23 pm
  
  The Dr. Sky
  Subscriber
  
  My IT people were able to identify the culprit and resolve all System Coupling issues caused by the 2023 Ansys releases by simply deactivating the IPv6 protocol in the ethernet properties. Turning off IPv6 is the only way to have System Coupling connect all participants in 2023R1 and 2023R2, when the workstation belongs to a domain. It is unfortunate that Ansys was not able to help on such a widespread bug.
- September 22, 2023 at 6:50 pm
  
  MangeshANSYS
  Ansys Employee
  
  Hello you can set this environment variable before running system coupling to ensure it runs on localhost ANSYS_RPC_LOCALACCESSONLY=1 I hope this is helpful

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System Coupling hostname issue in ANSYS 2023R1 and 2023R2

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