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

A PCS 7 V9.1 user reported that NetToPLCSim worked after changing the startup order: start NetToPLCSim before Siemens software so it can capture TCP port 102, then start S7-PLCSIM, load the program, configure NetToPLCSim and start its server. The NetToPLCSim project describes its S7o version as a network bridge for STEP 7 S7-PLCSIM V5.4/5.5, while Siemens lists S7-PLCSIM V5.4 SP8 Update 1 with PCS 7 V9.1. This is a reported combination, not Siemens certification of the third-party tool.

Compatibility: What the Evidence Supports

PCS 7 V9.1's Readme lists S7-PLCSIM V5.4 SP8 Update 1 as the PCS 7 component version and says PLCSIM supports simple application tests without AS hardware. NetToPLCSim's project page describes the S7o branch as a TCP/IP network extension for Siemens PLCSIM Step 7 V5.4/5.5 that exchanges data through the S7ONLINE interface. Those ranges overlap, but Siemens' component list does not test or approve NetToPLCSim. The source author reported successful operation after using a different startup order; the exact NetToPLCSim and PLCSIM builds used in that case are not recorded.

Method: Start NetToPLCSim Before Siemens Software

The following sequence is reported by the NetToPLCSim maintainer in the project discussion and matches the PCS 7 forum's successful case. It assumes a supported legacy STEP 7 PLCSIM configuration; interface labels and privilege requirements can differ by build.

Restart the engineering PC or virtual machine to begin from a clean state.
Before opening Siemens software, start NetToPLCSim with the required administrative rights. Leave its server unconfigured while it captures TCP port 102.
Start the Siemens engineering software and S7-PLCSIM. Load the intended simulated PLC program.
Configure NetToPLCSim for the simulated PLC and intended network interface, then start the NetToPLCSim server.
Verify the connection from the intended PCS 7/WinCC client and check that the simulation values respond as expected.

The NetToPLCSim maintainer describes this as an operating sequence based on experience, not a PCS 7 manufacturer-supported compatibility guarantee.

After Simulation: Restore the Real-PLC Connection

The original discussion recommends restarting the computer after the test before connecting to a real PLC. Siemens' PCS 7 V9.1 Readme independently warns that after using PLCSIM, it may be necessary to re-establish the real connection and recompile changes made to the relevant AS, including the real connection to the OS. Before switching to a live controller, close the simulation workflow, confirm the engineering station's configured interface and target address, and follow the plant's approved connection procedure. Do not rely on a simulator connection test as proof that the correct real controller is selected.

Troubleshooting the Startup Sequence

If NetToPLCSim cannot capture the port or connect to PLCSIM, verify that it was started before other Siemens applications, that the expected PLCSIM instance is running, and that the correct network interface and simulated PLC are selected. Capture the NetToPLCSim version, S7-PLCSIM version, Windows version, port-capture result and connection messages. The maintainer's project discussion also notes that network connectivity in a virtual machine matters; a disconnected virtual adapter can prevent communication. Do not generalize compatibility from another project using TIA Portal or newer PLCSIM versions.

Verification

Confirm that the NetToPLCSim server indicates an active connection to the intended PLCSIM instance and that the PCS 7/WinCC client can read and write only the expected test data. Then confirm that PCS 7's real connection is restored according to the site procedure before using a physical PLC. These checks verify the communication path used in the test; they do not validate process behavior or make the third-party bridge suitable for production control.

Limitations and Operational Precautions

NetToPLCSim is a third-party simulation bridge. Its project page and community instructions are not Siemens product qualification documents. The ticket omits the exact NetToPLCSim build, Windows build, PC interface configuration and detailed test scope. Use this arrangement only in an isolated engineering or test setup with simulated logic and controlled network access. Prevent accidental connection to a live controller, verify target identity before any online action, and restore the site's normal engineering-station communication state after simulation.

Engineer FAQ

Does Siemens certify NetToPLCSim for PCS 7 V9.1? The cited Siemens Readme lists the S7-PLCSIM component version but does not mention or certify NetToPLCSim.

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

What startup sequence worked in the report? Start NetToPLCSim first so it captures port 102, then start Siemens software and PLCSIM, load the program, configure the bridge and start its server.

Should the workstation be restarted before connecting to a real PLC? The ticket recommends a restart after simulation, and Siemens notes that real connections may need to be re-established after PLCSIM use. Follow the approved site process and confirm the target.

Technical References

Siemens, PCS 7 Readme V9.1 (Online), §4.1.4 “Using S7 PLCSIM” and §5 component table: https://cache.industry.siemens.com/dl/files/270/109780270/att_1057737/v1/pcs7-readme_en-US.pdf
NetToPLCSim project page and S7o package information, describing the STEP 7 PLCSIM V5.4/5.5 network extension: https://sourceforge.net/projects/nettoplcsim/files/
NetToPLCSim maintainer discussion with the startup order and port 102 capture procedure: https://sourceforge.net/p/nettoplcsim/discussion/912717/thread/da0fd01029/

The Siemens Readme, NetToPLCSim project page and maintainer discussion were opened. The project-specific startup sequence is community guidance; Siemens does not certify the bridge in the cited Readme.

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