Webserver and FlexSim 25.0.2 - Client does not send/receive TCP data

Hello,

following the instructions and troubleshooting found in the answers a webserver was configured and correctly points to FlexSim 25.0. However, when a process is launched by the Experimenter, there is a request to the webserver to create the child instances (terminal window), but nothing else happens and the FlexSim interface (client) gets frozen. The only way to stop it is to kill the FlexSim process.

I am able to run the model directly from the server, but not from the client FlexSim experimenter interface.

Would you please confirm the configurations or infer what would be the reasons for this problem?

Thank you.

Sources used:

https://answers.flexsim.com/articles/53302/using-amazon-web-services-for-distributed-experime.html

https://answers.flexsim.com/articles/66639/distributed-experiments-or-optimizations.html

https://answers.flexsim.com/questions/163904/question-about-webserver-24.html

Software Version:

FlexSim 25.0.2

· 10

Gui Vaccaro commented · Feb 07 2025 at 11:35 AM

@Jordan Johnson , apologies for asking directly.

Is there any possibility for you to help me with this issue? I am asking as you were the author of the original document.

Thank you and apologies again.

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Jordan Johnson ♦♦ Gui Vaccaro commented · Feb 07 2025 at 2:43 PM

The main test is to run the webserver on your local machine and set your cloud computing to localhost or 127.0.0.1. If that does not work, there may be an issue with the software. If that works but the remote version does not work, then there is some firewall, connection, or installation issue.

Another thought: it may look like nothing is happening, but if you open the task manager on the remote computer, do new FlexSim processes appear? There should be one for each CPU. If the processes appear, you may just need to wait. FlexSim transfers the model to each child process one at a time (we'd like to improve that at some point), but with many CPUs, it can take a couple of minutes to finally get started.

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Gui Vaccaro Jordan Johnson ♦♦ commented · Feb 07 2025 at 8:02 PM

Hi, @Jordan Johnson , thank you. I can confirm that the connection happens and the FlexSim instances are created. In simpleton term, that is the "HTTP work". What does not happen is the client being able to upload data to the instances. In one of the attempts with the VPN and VPC teams, we got a message in FlexSim's console saying "The remote server was unable to provide a TCP port..." We could not replicate that though (to our perplexity).

I was recommended to ask you gentlemen if is there any configuration on the server side that should ensure ports 9000-... to be opened (besides the security group).

It is either that or some blockage on the VPN...

Thank you again for all your support.

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Jason Lightfoot ♦♦ commented · Feb 07 2025 at 11:58 AM

Hi Gui - the replications communicate progress through port 9000+ , so you could check that communication via those ports is allowed through the firewall/network security.

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Gui Vaccaro Jason Lightfoot ♦♦ commented · Feb 07 2025 at 1:59 PM

Hi, @Jason Lightfoot ,

there is no communication, unfortunately. The problem seems to be the same as here (https://answers.flexsim.com/questions/136085/flexsim-distributed-computing-on-webserver-is-not.html), but unfortunately, there is no solution explained there.

I tested communications for several TCP ports and they are not happening.

The headless instances are created when the first contact is made by the client IP, but they remain empty and no calculation happens (CPU usage/instance ~ 0). It seems the models are not uploaded. That is all I could speculate.

Thank you for any help.

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Jason Lightfoot ♦♦ Gui Vaccaro commented · Feb 07 2025 at 2:26 PM

But is communication through those ports restricted or allowed by your network security/firewall?

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