Problem Overview: Server Mismatch When Opening WinCC Flexible RT Project
When an integrator or maintenance engineer receives a copy of a WinCC flexible 2008 HMI project from a machine builder, the project may fail to open on the receiving configuration PC with a generic "server mismatch" dialog. The error typically appears the moment WinCC flexible 2008 SPx attempts to dereference the integrated project container that links the HMI configuration to the underlying STEP 7 project.
The root cause is almost always a STEP 7 version mismatch between the configuration PC that originally compiled the project and the PC attempting to open it. Because WinCC flexible stores HMI-to-PLC tag references in a binary index tied to the originating STEP 7 / SIMOTION / iMap log database (log.idf), the receiving PC must host a STEP 7 version that can read or reconstruct that index. A project built on STEP 7 V5.4 will not open cleanly on STEP 7 V5.3 even though WinCC flexible 2008 itself can be installed on either.
*.fwx) cannot be edited. Only the configuration source (*.hmi, *.log, *.ldf, etc.) can be reopened in WinCC flexible. If only a compiled RT file exists, reverse engineering is not possible; the configuration source must be requested from the OEM.
Distinguishing WinCC flexible vs. WinCC flexible RT
Engineers regularly confuse the configuration tool with the runtime. The distinction matters because it dictates what can and cannot be edited.
| Component | File Extension | Editable | Purpose |
|---|---|---|---|
| WinCC flexible Configuration |
*.hmi (project) |
Yes | Source project edited in WinCC flexible ES |
| WinCC flexible Runtime | *.fwx |
No (binary, compiled) | Run-only file loaded on Panel / RT PC |
| WinCC flexible Log Database |
log.idf / *.log
|
Auto-managed | Index linking HMI tags to STEP 7 symbols |
| WinCC flexible Archive |
*.ard or *.zip
|
Yes (after Retrieve) | Compressed, version-portable project bundle |
| SIMATIC WinCC (TIA portal predecessor for PC) | *.mcp |
Yes | PC-based SCADA, separate product line |
If the deliverable is a single *.fwx file, the engineer cannot open it in WinCC flexible 2008 for editing. They must request the original configuration source from the machine builder (OEM).
Root Cause: STEP 7 Version Mismatch and the log.idf File
The log.idf file (also referenced as *.log or S7log.idf depending on the version) is created when a WinCC flexible project is first integrated into a STEP 7 project. It stores the cross-reference map between HMI tags and STEP 7 symbols (DBs, M-bits, I/Q addresses, etc.). On every subsequent open, WinCC flexible consults this file to rebuild tag-to-address mappings.
When the originating PC used STEP 7 V5.4 and the receiving PC has only STEP 7 V5.3 + SP3 installed, the IDF container version is forward-compatible only to a point. STEP 7 V5.4 introduced internal changes to the log database schema that V5.3 cannot decode, producing the server mismatch dialog at project open.
STEP 7 / WinCC flexible Compatibility Matrix (Relevant Pairs)
| WinCC flexible Version | STEP 7 V5.3 | STEP 7 V5.4 + SPx | STEP 7 V5.5 |
|---|---|---|---|
| WinCC flexible 2004 | Supported | Not supported | Not supported |
| WinCC flexible 2005 | Supported | Limited | Not supported |
| WinCC flexible 2007 | Supported | Supported | Limited |
| WinCC flexible 2008 | Supported | Supported | Supported |
| WinCC flexible 2008 SP2 | Supported | Supported | Supported |
| WinCC flexible 2008 SP3 | Supported | Supported | Supported |
Locating the log.idf / Project Files on Disk
The receiving engineer cannot see the log file inside WinCC flexible because the project never opens. Locate it manually with Windows Explorer:
- Open the project folder delivered by the OEM (typically a directory tree named after the S7 station).
- Search for
log.idf,*.idf,*.log, andS7log.idfat the project root and one level deep. - Standard location under Windows XP/7:
C:\Documents and Settings\<User>\Application Data\Siemens\Automation\WinCC flexible\<ProjectName>\. - Under Windows 7/10:
C:\Users\<User>\AppData\Roaming\Siemens\Automation\WinCC flexible\<ProjectName>\or%LOCALAPPDATA%\Siemens\Automation\WinCC flexible\. - If the project was opened at any point, look in
%LOCALAPPDATA%\Siemens\Automation\WinCC flexible\Log\for cached IDF segments.
After locating log.idf, the recommended first step is to rename it (do not delete yet) and let WinCC flexible regenerate it on the next successful open.
Solution 1: Archive / Retrieve (Recommended)
The cleanest workaround for the version-mismatch problem is to use WinCC flexible's built-in Archive and Retrieve functions. These re-serialize the project into a self-contained, version-neutral container that can be opened on any host with the matching WinCC flexible version.
Archive on the Source PC
- In WinCC flexible 2008 on the originating PC: Project > Archive.
- Choose the S7-integrated project (the one that includes the WinCC flexible part).
- Select the output path and confirm; WinCC flexible creates
<ProjectName>.ard.
Retrieve on the Target PC
- Copy the
.ardarchive to the target PC. - In WinCC flexible 2008: Project > Retrieve.
- Browse to the
.ardfile and select a working directory. - WinCC flexible extracts the HMI configuration and rebuilds the
log.idfagainst the locally installed STEP 7 version (V5.3 in this scenario).
Solution 2: Re-create log.idf Manually
If Archive/Retrieve is not possible (e.g., the source PC is gone but the receiving PC still has the partially-extracted project tree), perform a manual log reset:
- Close WinCC flexible.
- Navigate to the project directory (see locating steps above).
- Rename
log.idftolog.idf.bak(do not delete). - Rename any companion
*.logfiles in the same directory tree. - Re-open the project in WinCC flexible 2008. The tool will detect the missing IDF and offer to recreate it by scanning the STEP 7 project for symbol references.
- Confirm regeneration. Depending on the project size, this takes 30 s to 5 min.
If the dialog still reports server mismatch, the underlying STEP 7 project (the *.s7p) must also be opened first in the local STEP 7 V5.3 to force its own log database to migrate.
Solution 3: Upgrade or Downgrade STEP 7 to Match the Source
If the project is mission-critical and the engineer cannot lose tag references, the most reliable path is to install the matching STEP 7 version on the PC. Both upgrades and downgrades are supported under specific conditions:
| Source STEP 7 | Target STEP 7 | Migration Path | Risk |
|---|---|---|---|
| V5.3 | V5.4 + SP5 | In-place upgrade, IDF auto-upgrades | Low |
| V5.4 | V5.3 + SP3 | Requires Archive/Retrieve via a V5.4 staging PC | Medium - downgrades are not direct |
| V5.4 | V5.5 + SPx | In-place upgrade supported by V5.5 installer | Low |
| V5.5 | V5.4 | Not directly supported; use intermediate PC | High |
Solution 4: Configure the RT Loader for Transfer to a Visualization PC
If the deliverable is a runtime file (*.fwx) that must be loaded onto an RT PC, configure the RT Loader on the target PC. This is documented in the official Siemens support entry Entry ID 29054992 - Configuring the RT Loader for WinCC flexible Runtime transfer.
- Install WinCC flexible Runtime on the visualization PC matching the SP level used at compile time.
- Start WinCC flexible RT Loader from
Start > SIMATIC > WinCC flexible > RT Loader. - In the Transfer Settings tab, set the transfer mode to Manual transfer or Automatic depending on operator policy.
- Confirm the Source PC entry points to the configuration PC's IP or hostname and that TCP port 2308 is reachable (default for WinCC flexible / ProSave transfer).
- Disable the Windows Firewall rule blocking inbound 2308 on both PCs, or add a scoped allow rule for the engineering subnet only.
- On the configuration PC, in WinCC flexible ES, choose Transfer > Transfer Settings, enable Remote Transfer, and enter the target RT PC's IP.
- Initiate transfer. The RT Loader window on the target PC will display progress and completion status.
Verification Checklist After Resolving the Mismatch
Use this matrix to confirm the project opens cleanly and the runtime will load without further errors.
| Check | Expected Result | Pass/Fail Criteria |
|---|---|---|
| Project opens without server mismatch dialog | Clean open, no warnings | Pass = opens; Fail = dialog reappears |
| log.idf regenerated | New file timestamp matches open time | Pass = mtime recent; Fail = file absent or unchanged |
| Cross-references resolve | Project > Cross-references shows green tags | Pass = no red marks; Fail = unresolved symbols |
| Compile project | Project > Compiler > Check Consistency returns 0 errors | Pass = 0 errors, 0 warnings; Fail = any error |
| Generate RT file | Project > Compiler > Generate Runtime produces *.fwx
|
Pass = file produced; Fail = compile error |
| Transfer to Panel / RT PC | Transfer completes in < 5 min for typical project | Pass = success; Fail = transfer timeout / S7-IFB error |
| Online tag test | Start Runtime, force one tag in PLC, verify HMI updates | Pass = HMI reflects value; Fail = value static |
Troubleshooting Matrix for Common Companion Errors
| Symptom | Likely Cause | Remedy |
|---|---|---|
| "Server mismatch" on open | STEP 7 version mismatch (log.idf incompatible) | Archive/Retrieve or rebuild log.idf |
| "Cannot find STEP 7 project" | Path relocation after Retrieve | Reintegrate via Options > WinCC flexible Settings |
| Tags show red exclamation mark | STEP 7 optional package missing on target PC | Install matching optional package or remap tags |
| Transfer fails with S7-IFB error | Automation License Manager not running | Start S7LMT.exe and verify license stick |
| Runtime starts but variables are static | MPI/PROFIBUS/Ethernet connection to PLC broken | Verify PG/PC interface selection in Set PG/PC Interface |
| "Version of WinCC flexible too old" | Target PC has 2005 ES, source used 2008 SP2 | Upgrade to WinCC flexible 2008 SP2 or later |
| Archive extracts but Retrieve fails | Insufficient disk space or write permission on project path | Run as administrator, free 2 GB minimum |
Preventive Recommendations for Maintenance Teams
To avoid future version-mismatch incidents on transferred machines, enforce a project-handover policy:
- Request both the
*.s7pSTEP 7 project and the WinCC flexible source (*.hmi) on every new machine delivery. - Ask the OEM for a single
.ardarchive of the integrated project - this is the most portable format. - Record the exact versions of WinCC flexible and STEP 7 used at commissioning in the machine's technical file.
- Maintain at least one engineering PC with the same version pair as the OEM; this preserves log.idf compatibility for any future field service.
- Subscribe to the Siemens SIOS support portal for current SP release notes and known compatibility restrictions for WinCC flexible 2008.
What causes the WinCC flexible "server mismatch" error when opening a project?
The error is caused by a mismatch between the STEP 7 version used to compile the original project (typically V5.4) and the version installed on the PC attempting to open it (typically V5.3). The log.idf index that links HMI tags to STEP 7 symbols cannot be decoded by the older version.
Where is the log.idf file located for a WinCC flexible project?
By default, log.idf is in the WinCC flexible project directory, typically under %LOCALAPPDATA%\Siemens\Automation\WinCC flexible\<ProjectName>\ on Windows 7/10 or C:\Documents and Settings\<User>\Application Data\Siemens\Automation\WinCC flexible\ on Windows XP.
Can a WinCC flexible Runtime file (*.fwx) be edited in WinCC flexible?
No. The *.fwx runtime file is a compiled binary and cannot be opened or edited in WinCC flexible ES. Only the configuration source (*.hmi) can be edited, which must be requested from the original machine builder.
Does the Archive/Retrieve function fix STEP 7 version mismatch issues?
Yes. Archive on the source PC produces a self-contained .ard container. Retrieving on the target PC rebuilds the log.idf against the local STEP 7 version (e.g., V5.3), eliminating the server mismatch error on subsequent opens.
What TCP port does the WinCC flexible RT Loader use for transfer?
The RT Loader uses TCP port 2308 by default for file transfer from the configuration PC to the visualization PC. This port must be reachable on both PCs and allowed through Windows Firewall for the engineering subnet.