I have set up a proxy server as a middleman to connect to our AS/400 system.
In my .ws file, I have manually configured the Host to the proxy IP and the Port to the proxy port.

When I try to connect using the .ws file in PC5250, the session does not start and displays the "server not started or blocked by firewall" message. However, if I manually run a Telnet command from the Windows Command Prompt to the same proxy IP and port, the connection works successfully.

Could you please check why the connection through the .ws file is failing while a direct Telnet works fine?

error:

properties

working CMD:

First, please install ACS 1.1.9.9, from there we'll see again

Agree with Peter's advice here, use the latest ACS package that will include the updated security patches fixed within the IBM connection servers. 

Then, port 23 (non ssl telnet) / 992(ssl telnet) might be open on your network which is a direct connection to the 5250 data stream minus the advanced 5250 features. This albeit a basic connection test isnt relaiable as you do need more servers access on other ports like 

etc. 

the error box you see in IBM i Client Access session most likely deals with (Signon Verification - as-signon ) being blocked. 

see here for the reference on ports that you need enabled : 
https://www.ibm.com/support/pages/node/644775


once you have ACS installed, during the configuration you have an option to test both the NON-SSL and the SSL ports during verification to allow you to see what is open / accessible or not. 

then your last troubleshooting step would be to confirm with the IBM i admin to check if all relevant host servers are started, most dont start that automatically either due to security posture hardening or different command startup during an IPL. 

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Marius le Roux theIBMiGuy
Owner , IBM i Consultant & Technology Strategist
MLR Consulting
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