https://forge.codesys.com/forge/talk/Engineering/thread/a449d5e34d/2026-01-06T02:13:37.054000ZRecent posts to CODESYS OPC UA Security: HMI Client Not Receiving Server Certificate2026-01-06T02:13:37.054000Z2026-01-06T02:13:37.054000Zbaott569https://forge.codesys.com/u/baott569/https://forge.codesys.come1492611f60fedf5e48ee38a3d23b225fec5255c

<div class="markdown_content"><p><strong>Hello everyone</strong>,</p> <p>I am currently using <code>OPC UA in CODESYS</code> with the security mode <code>BASIC256SHA256</code> – <code>Signed and Encrypted</code>.<br/> The <code>OPC UA Server</code> is running on an <code>RTE CX</code> device, and the <code>HMI</code> is running on another computer.</p> <p>I have reviewed many CODESYS documents and successfully established communication when the security mode is set to <code>None</code> with <code>Anonymous login</code>. However, when security is enabled, the server does not provide its certificate for the CODESYS HMI client to trust.</p> <p>Interestingly, the client can send its certificate to the server, and <code>UAExpert</code> works normally, but the <code>CODESYS HMI client</code> does not receive the server certificate.</p> <p>Can anyone help clarify what I might be missing? I have been stuck on this issue for three days. If I missed or misconfigured any step, please let me know.</p> <p>I believe I am stuck at step 15 in the following CODESYS guid<img alt="" src="https://"/>e:</p> <blockquote> <p>Encrypting the Communication of a Data Source OPC UA Client<br/> <code>https://content.helpme-codesys.com/en/CODESYS%20Communication/_cds_encrypt_communication_data_sources_opc_ua_client.html</code></p> </blockquote> <p>Thank you very much.</p></div>