How to Start NetToPLCSim with PCS 7 V9.1 and S7-PLCSIM

NetToPLCSim can be used in a PCS 7 V9.1 simulation setup when the installed S7-PLCSIM version and startup sequence are suitable, but this is not a Siemens compatibility guarantee for the third-party bridge. A reported working sequence is to restart Windows, let NetToPLCSim acquire TCP port 102 before starting Siemens applications, then load S7-PLCSIM and start the bridge server. PCS 7 V9.1's Readme lists S7-PLCSIM V5.4 SP8 Update 1; the ticket does not identify its installed build.

Applicability and prerequisites

PCS 7 V9.1 documentation identifies S7-PLCSIM V5.4 SP8 Update 1 as the tested simulation component. NetToPLCSim is a third-party application; its use with this exact PCS 7 configuration is not covered by that Siemens compatibility statement. Confirm the installed PLCSIM version, the target CPU/project configuration, and the NetToPLCSim release before relying on the setup.

Why startup order matters

The NetToPLCSim maintainer's support discussion describes contention for TCP port 102 with Siemens' S7DOS service and recommends starting NetToPLCSim before Siemens software in the discussed configuration. This explains why launching PLCSIM first can prevent the bridge from acquiring the port. It is a reported workaround, not a universal requirement for every NetToPLCSim or Siemens software release.

Procedure

Use this sequence only on an engineering or test computer where stopping/restarting the relevant Siemens service is acceptable:

Save work and restart Windows to begin from a known service state.
Before opening SIMATIC Manager, PCS 7 applications, or PLCSIM, start NetToPLCSim and use its port-acquisition behavior to obtain TCP port 102. Confirm the program reports that it acquired the port; do not manually terminate unrelated processes.
Start the Siemens engineering software and S7-PLCSIM. Load the simulation project/program using the normal version-appropriate workflow.
Configure the NetToPLCSim connection for the running PLCSIM instance and start its server.
Connect only the intended test client and perform the project-specific communication checks described below.

Expected result and diagnosis

The bridge should report a usable connection to the simulated PLC, and the client should be able to establish communication with the configured simulation endpoint. If port acquisition fails, stop and inspect the local port/service ownership using approved IT procedures; do not infer that changing port ownership or disabling a Siemens service is safe for the installed engineering environment. If the bridge starts but the client cannot communicate, check the configured interface, address, rack/slot or connection parameters required by that client and simulation setup.

Returning to a physical PLC

The source reports restarting the computer before connecting to a real PLC after testing. Treat this as a prudent reset for the specific workflow, not a product guarantee. Close the bridge and simulation, restore the site's normal engineering communication setup, and confirm the selected PG/PC interface and target address before any online operation. Do not download to a production controller as a connectivity test.

Verification

Verify the simulated connection end to end with a non-production client and known, noncritical project data. Confirm the client is communicating with the intended simulated CPU rather than a physical controller, and verify live values or a harmless read operation rather than relying only on a server-start indication. Recheck the engineering interface before later physical PLC work.

Limitations and Operational Precautions

The source does not state the NetToPLCSim build, the installed S7-PLCSIM build, Windows version, or project configuration. Siemens' PCS 7 V9.1 Readme establishes a PCS 7-tested PLCSIM version but does not certify NetToPLCSim. The sequence is supported by maintainer/community troubleshooting material and the report in this case; validate it in a non-production environment. Avoid manually disabling services or changing communication settings on a plant engineering station without change control.

Engineer FAQ

Does PCS 7 V9.1 officially support NetToPLCSim? The cited PCS 7 Readme lists the tested S7-PLCSIM component, not NetToPLCSim. Treat the bridge as third-party.

Which S7-PLCSIM version does the PCS 7 V9.1 Readme list? S7-PLCSIM V5.4 SP8 Update 1.

Why start NetToPLCSim before PLCSIM? The maintainer's troubleshooting discussion describes TCP port 102 ownership conflict involving S7DOS; the startup order is a reported way to resolve it.

Does a running bridge prove the project is communicating correctly? No. Verify the client-to-simulation path using safe, observable project data.

Should the same computer connect directly to a plant PLC immediately afterward? Restore the normal communication configuration and verify the selected interface and target before any online action; the source recommends a restart.

Technical References

Siemens, PCS 7 Readme V9.1 (S7-PLCSIM version and compatibility context): https://support.industry.siemens.com/cs/attachments/109780270/pcs7-readme_en-US.pdf
NetToPLCSim maintainer discussion, NetToPLCSim with S7-PLCSIM V5.4 incl. SP8 (reported port-acquisition/startup sequence): https://sourceforge.net/p/nettoplcsim/discussion/912717/thread/6bb122d7/

How to Start NetToPLCSim with PCS 7 V9.1 and S7-PLCSIM