Resolving 'RT Station Not Obtainable' During OS Client Download in SIMATIC PCS 7

In SIMATIC PCS 7, the error 'RT station not obtainable' encountered when downloading an OS Client project from the Engineering Station (or combined ES/OS Server) indicates that the remote procedure call (RPC) or DCOM handshake between the stations has failed. Even if the client PC responds to ping and network file sharing operates normally, WinCC remote engineering downloads require specific network infrastructure: the Windows Firewall must permit WinCC communication (or be disabled for testing), SimaticShell on both stations must be explicitly bound to the Terminal Bus network adapter, bidirectional host name resolution must be verified in the hosts/lmhosts files, and the logged-in Windows user must belong to the SIMATIC HMI user group on both machines.

DCOM and RPC Architecture of Remote WinCC Station Downloads

In SIMATIC PCS 7, transferring an Operator Station project from the Engineering Station to target OS Servers and OS Clients is executed via the AS-OS Engineering download utility (PLC -> Download). Unlike basic Windows file copying, a WinCC station download is an active, multi-stage transaction:

Remote Handshake: The ES queries the target PC's CCProjectMgr.exe service via Microsoft Distributed Component Object Model (DCOM) over TCP port 135 to check project status.
Project Closure: If a project is open, DCOM commands the target station to close the database.
Database File Transfer: Project files (.mdf, .ldf, .pdl) are copied over Windows network shares (SMB).
Database Registration: The ES executes remote registration scripts on the target station's Microsoft SQL Server instance.

If the initial DCOM handshake fails or the target station's WinCC project manager cannot be contacted, SIMATIC Manager aborts the transfer with the error: 'RT station not obtainable'.

Diagnostic Causes of 'RT Station Not Obtainable'

Because basic ICMP ping packets and manual Windows file copies do not exercise DCOM security or dynamic RPC ports, a system can appear fully networked while remote WinCC downloads fail completely:

Diagnostic DimensionConfiguration IssueTechnical BottleneckCorrective Engineering ActionWindows FirewallActive firewall on OS ClientDynamic RPC ports and TCP port 135 blockedRun Siemens Security Controller / permit WinCC rulesSimaticShell BindingBound to wrong network adapterTerminal Bus discovery frames not routed to OS ClientIn SimaticShell Settings, select Terminal Bus adapterHost Name ResolutionNetBIOS broadcast blocked across subnetsDCOM fails to resolve IP to NetBIOS hostnameAdd static IP and Computer Name to hosts fileUser Group PermissionsWindows user missing from SIMATIC HMIDCOM Access Denied on remote RPC interfaceAdd Windows user to SIMATIC HMI and AdministratorsTarget OS Path SyntaxUnresolvable UNC path in OS PropertiesTarget directory points to local drive letter instead of UNCConfigure UNC path: \\OS_CLIENT_01\WinCC_Project\

The presence of objects like WinCC.LicenseLimit in SimaticShell is a normal licensing reflection and does not cause download failures.

Step-by-Step Resolution and Network Configuration Workflow

To resolve 'RT station not obtainable' and achieve smooth OS Client downloads, execute the following technical workflow:

Configure SimaticShell Network Binding on Both PCs: Open Windows File Explorer -> This PC -> SimaticShell. Right-click SimaticShell and select Settings.... Verify that the selected network adapter is strictly the Terminal Bus physical card on both the ES/Server and the OS Client. Ensure both stations display blue active computer icons in the SimaticShell browser.
Configure Windows Firewall and Security Controller: On both machines, launch the Siemens Security Controller from the Windows Start Menu. Click Repeat Settings to automatically open all required DCOM, SQL Server, and WinCC ports. For diagnostic isolation, temporarily disable the Windows Firewall on the private/domain network profile.
Verify Bidirectional Name Resolution in Hosts File: Open C:\Windows\System32\drivers\etc\hosts as Administrator. Add static mapping lines for both machines:

192.168.2.10    ES_SERVER_01
192.168.2.20    OS_CLIENT_01

Open Command Prompt on both stations and verify that ping -a <IP> returns the exact matching hostname.

Align Target OS Directory Path: In SIMATIC Manager, right-click the OS Client object and select Object Properties. Under the Target OS and Standby OS Computer tab, ensure the target path is defined as a UNC share: \\OS_CLIENT_01\Project_Share.
Execute Download: Right-click the OS Client object in SIMATIC Manager and select PLC -> Download. Select Entire WinCC Project.

Verification

Verify remote engineering connectivity and download integrity through these diagnostic steps:

Download Progress Bar Check: Initiate the download from SIMATIC Manager. Confirm that the progress dialog displays 'Copying files to target station...' without pausing or triggering DCOM timeout alerts.
Target Folder Audit: On the OS Client PC, open the shared project directory. Confirm that the client project files (.mcp, .dcf) are newly timestamped and populated.
WinCC Client Startup: Launch WinCC Explorer or Autostart on the OS Client. Confirm that the client project opens cleanly and connects to the OS Server package.

Limitations and Operational Precautions

When architecting OS Client-Server networks, adhere to these operational safeguards:

Symmetric Windows User Credentials: The logged-in Windows user account on the ES must exist with the identical username and identical password on the OS Client, and must be a member of the local SIMATIC HMI user group on both stations.
Terminal Bus vs Plant Bus Isolation: Never bridge or route OS Client downloads across the Plant Bus. OS Client communication is strictly confined to the Terminal Bus.
Avoid Combined ES/OS Server in Large Plants: While combining an ES and OS Server onto a single computer is supported for small package units, standard industrial practice recommends separate physical hardware for the Engineering Station to prevent engineering activities from impacting real-time server performance.

Engineer FAQ

Why can I ping the client and copy files manually if the station is 'not obtainable'?

Ping uses ICMP, and manual file copying uses basic SMB file shares. WinCC remote downloads require DCOM (RPC) communication over TCP port 135 to command CCProjectMgr.exe. A firewall or SimaticShell misconfiguration blocks DCOM while allowing ping.

Does missing an OS Client license prevent project download?

No. Missing licenses will cause WinCC Runtime to display demo mode popups, but license state does not block SIMATIC Manager from downloading the project files.

What is the function of the Siemens Security Controller?

The Security Controller is an administrative tool provided on the PCS 7 DVD that automatically configures Windows firewall rules, DCOM permissions, and registry security policies required for PCS 7 operation.