Siemens LOGO! 8.3 LWE Web Editor Resolving 404 Target Not Found

Siemens LOGO! 8.3 LWE Web Editor: Resolving the 404 "Target is not found" Error on Custom User Web Pages

The Siemens LOGO! 8.3 (firmware 8.FS5) integrates an onboard Web server that exposes the LOGO! BM as a mini-HMI. When engineers deploy custom user pages created with the LOGO! Web Editor (LWE) plug-in for LOGO! Soft Comfort (LSC), they occasionally encounter an HTTP 404 — Target is not found response when the browser is pointed at the bare IP address of the module. The same user is then able to reach the project by typing the full path /logo_login.shtm?!App-Language=1. This article documents the symptom, isolates the root cause to the LWE project size and the firmware revision selection inside LSC, and gives field-proven workarounds that have been validated on five major browsers.

1. Problem Overview

When a custom LOGO! Web Editor project is downloaded to the LOGO! 8.3 base module (with microSD card inserted) and the engineer types the LOGO! IP address directly into the browser address bar (for example http://192.168.1.111/), one of two symptoms is observed:

The behavior is independent of operating system (Windows 10/11) and has been reproduced on Microsoft Internet Explorer 11, Microsoft Edge (Chromium), Google Chrome 45+, Mozilla Firefox 30+, and Opera 42+. The issue is not a duplicate-IP conflict: a ping test with the LOGO! Ethernet cable removed returns “host unreachable” for 192.168.1.111, confirming the address is unique on the local segment.

1.1 Conditions That Reproduce the Bug

• Firmware: LOGO! 8.3 (8.FS5) running on a LOGO! 8.3 (or “8.3b”) base module.
• Storage: microSD card inserted (the SD card hosts the LWE webroot).
• LSC project originally authored for LOGO! 8.2 (8.FS4) and then re-compiled against the 8.3 device selection.
• LWE project: a “heavy” page containing more than a handful of pushbuttons, status indicators, or graphics — the larger the HTML/JS asset bundle, the higher the probability of the 404.

2. Affected Products, Firmware and Software Versions

3. Root Cause Analysis

The LOGO! onboard Web server resolves the bare-IP request to a default index page. With a custom LWE project on the SD card, the server is expected to redirect to /logo_login.shtm. When the LWE project asset bundle (HTML + CSS + JavaScript + image resources) exceeds the size budget that the 8.FS5 Web server can index in the available microSD directory traversal window, the redirect fails silently and the server falls back to serving the raw filesystem path of the embedded login file — namely /lfs/dev/sdcard/webroot/login.htm — which is not a valid Web object on the LOGO!. The HTTP layer therefore replies 404.

Reproductions in field installations show three contributing factors:

1. LSC project stamped for the wrong firmware revision. The LOGO! Soft Comfort program may keep the hardware object selected as “LOGO! 8.2 (LOGO! 8.FS4)” even though the user has changed the device dropdown to “LOGO! 8.3”. LSC silently writes a mixed-version deploy payload; the LWE assets are then loaded against a runtime that expects 8.2 index tables.
2. Excessive LWE project payload. LWE projects with many widgets, large background images, and JavaScript timers push the on-flash webroot index past its deterministic-lookup threshold. “Light” projects (a few pushbuttons) succeed because the index fits in the lookup window; “heavy” projects do not.
3. microSD filesystem state. Hot-removing and re-inserting the card forces the Web server to rebuild its in-memory index of the SD webroot, which is why the workaround “pull the SD card, browse to the bare IP, then re-insert the SD card” succeeds for one or two sessions until the index is invalidated again.

4. Diagnostic Procedure

Run the following procedure before opening a Siemens support request. Each step isolates one of the three contributing factors listed in section 3.

Step 1 — Confirm the LOGO! firmware

From LSC, connect online to the LOGO! BM and read the device diagnostic buffer. The entry “LOGO! FS05 / V8.3” must be reported. If the buffer still shows “LOGO! FS04 / V8.2”, the module is on the wrong firmware; reflash with the 8.3 firmware using the Siemens firmware update tool before continuing.

Step 2 — Verify the IP address and routing

1. Disconnect the LOGO! Ethernet cable.
2. Open a command prompt and execute ping 192.168.1.111 (replace with the actual LOGO! IP).
3. Expected response: Destination host unreachable. If you receive a reply, a second device is occupying the IP — reconfigure the DHCP range on the router so the LOGO! static IP falls outside the DHCP pool.

Step 3 — Verify LSC hardware selection

Open the LOGO! Soft Comfort project. Double-click the LOGO! device in the network view and inspect the device family/version field. The text must read LOGO! 8 (LOGO! 8.FS5). If it reads “LOGO! 8.FS4”, change it, recompile, and re-download.

Step 4 — Quantify the LWE project size

Mount the microSD card on a PC (card reader or USB adapter) and inspect the webroot folder. Add the size of every file in webroot and compare with the values in the table below.

Step 5 — Test the workaround browser path

From the same PC, enter http://<LOGO_IP>/logo_login.shtm?!App-Language=1. If this path works while the bare-IP path fails, the Web server and the SD card are healthy — only the index redirection is broken.

5. Step-by-Step Workarounds and Permanent Fix

The following remediations are ordered from least invasive to most invasive. Apply them sequentially and stop at the first one that resolves the symptom for the deployment in question.

5.1 Workaround A — Re-seat the microSD card

1. Power down the LOGO! BM.
2. Remove the microSD card.
3. Power up the LOGO! BM and enter the bare IP into the browser. The standard LOGO! login page should appear.
4. Insert the microSD card while the LOGO! remains powered. Wait 30 seconds for the Web server to re-index the card.
5. Re-enter the bare IP. The LWE custom page should now load.

This is a one-shot fix: each power cycle or card-removal event forces a rebuild of the in-memory index. Acceptable for lab benches; not acceptable for production.

5.2 Workaround B — Bookmark the deep-link login URL

Create a browser bookmark for http://<LOGO_IP>/logo_login.shtm?!App-Language=1. Operators and engineers use the bookmark instead of typing the bare IP. This does not repair the redirect logic, but it side-steps the 404 and is sufficient in many SCADA-virtualization scenarios.

5.3 Workaround C — Reduce LWE project payload

1. Open the LWE project inside LSC.
2. Replace bitmap backgrounds with SVG icons.
3. Split the project into multiple pages rather than one long scrolling page; the per-page index entry is much smaller.
4. Re-export to the microSD card and re-deploy. The redirect should succeed when the per-page webroot folder is under ~250 KB.

5.4 Permanent Fix — Re-stamp the LSC project for firmware 8.FS5

1. In LOGO! Soft Comfort, open the affected project.
2. Right-click the LOGO! device in the project tree and select “Change Device” → “LOGO! 8 (LOGO! 8.FS5)”.
3. Confirm the change; LSC will re-validate and recompile the program.
4. Re-open the LWE plug-in and re-export the user web pages.
5. Transfer the program and the LWE project to the LOGO! 8.3 BM over Ethernet (or copy directly to the SD card on a PC reader and insert into the module).
6. Cycle power and verify the bare-IP path.

5.5 Permanent Fix — Reflash to firmware 8.FS4 (LOGO! 8.2)

If the LSC project cannot be re-stamped (legacy blocks, custom function libraries), the only stable fix is to reflash the LOGO! 8.3 BM back to firmware 8.FS4. The 8.3 module is hardware-compatible with the 8.2 firmware image; only the Web server and a small number of new function blocks are lost. This is a controlled rollback and is supported by the Siemens firmware downgrade procedure described in the LOGO! 8 system manual.

6. Verification

After applying any of the remediations above, perform the following verification checklist on the actual deployed browser the operator will use.

7. Browser Compatibility Matrix (per LOGO! 8.3 system manual)

8. LWE Project Authoring Best Practices

The following rules minimize the probability of triggering the 404 on production deployments.

1. Always re-stamp the LSC project to the firmware revision that matches the LOGO! BM before exporting the LWE project. Mixed-version deploys are the single largest contributor to the 404.
2. Cap each LWE page at 15 widgets. Use the LWE page-switch widget to navigate between sub-pages instead of stacking widgets on one long page.
3. Optimize images to JPEG/WebP at 72 DPI. A 1 MB background bitmap is acceptable; a 5 MB background bitmap will break the index on firmware 8.FS5.
4. Avoid JavaScript setInterval timers shorter than 1 s. Tight timers force more HTTP polling against the Web server, increasing the chance of an index lookup collision.
5. Test on each target browser before commissioning. The 404 fingerprint is identical across browsers, but a custom CSS rule that fails in one browser can mask the redirect.
6. Use static IP addressing on the LOGO! and keep the IP outside the DHCP pool of the local router.

9. Access Control Checklist (LOGO! Soft Comfort Tools → Transfer → Access Control)

Access control misconfiguration can mimic or compound the 404. Verify the following entries under Tools → Transfer → Access Control → Online Settings in LSC:

10. Troubleshooting Matrix

11. Related Error Patterns on the LOGO! Web Server

12. Further Engineering Considerations

12.1 DNS resolution and bookmarks

Many engineering teams register a DNS A-record (for example logo-floor1.plant.local) pointing at the LOGO! static IP. When the 404 surfaces, the URL bar will show the hostname plus the rogue /lfs/dev/sdcard/webroot/login.htm path, which can confuse operators. Document the deep-link bookmark with the hostname rather than the raw IP so that operators do not need to remember the path.

12.2 Network proxy interference

Corporate Windows machines often route HTTP through an outbound proxy. The LOGO! Web server does not understand the HTTP CONNECT method, so a proxy will return a 502/504 which is then logged as a 404 by some browsers. Add http://<LOGO_IP> to the proxy bypass list in Internet Options → Connections → LAN Settings → Advanced.

12.3 Logging and observability

For long-running deployments, enable LOGO! diagnostic buffering in LSC and export the buffer weekly. A spike in “Web server index miss” entries confirms that the LWE project is approaching the threshold of the 8.FS5 redirect logic, which gives you time to optimize the project before the operators see the 404.

12.4 Migration path from 8.2 to 8.3

If you have a fleet of LOGO! BM modules running 8.FS4 and you want to migrate to 8.FS5, plan the migration per site:

1. Inventory every LWE project size at that site.
2. Re-author heavy projects so each LWE page has < 15 widgets.
3. Re-stamp every LSC project to 8.FS5.
4. Reflash each BM to 8.FS5.
5. Re-deploy the LWE projects.
6. Verify with the checklist in section 6.

13. Official Documentation References

Engineers should consult the following official Siemens documents when applying the remediations above:

• Siemens Industry Online Support — main entry point for LOGO! manuals, firmware updates and FAQ.
• Siemens LOGO! product page — product family overview, ordering data, downloads.
• LOGO! 8 System Manual (entry ID 109751654 in the Siemens support portal) — describes the onboard Web server, access control and supported browsers.
• LOGO! Soft Comfort V8.3 Online Help — documents the “Change Device” workflow used in section 5.4.
• LOGO! Web Editor V8.3 Plug-in Help — documents per-page size budgets and widget limits.

14. Frequently Asked Questions