Remoting¶

What is it ?¶

The remoting feature lets you to implement an additional interface to an existing FMU. There is 3 use cases: 1. Add a different bitness interface. For example, add a Windows 64bits interface to a existing 32bits only FMU. 2. Encapsulate the DLL of an existing FMU inside a dedicated process. This process will communicate with the simulation master. 3. Add a different OS interface. This feature is under study.

Rationale¶

Some OS can support 32-bits and 64-bits. Remoting feature adds a new interface to a existing FMU and let the user mix bitness between fmi-importer and the DLL contained into the FMU.

Limitation¶

Currently, only Co-simulation mode for FMI 2.0 is supported.

Available configurations¶

Implementation¶

Current implementation relies on Shared Memory and Semaphore. It is available on Windows and Linux only. Primary OS is Windows.

This version supports: - ONLY FMI 2.0, ONLY for co-simulation mode - Strings are NOT supported

Sequence Diagram¶

sequenceDiagram
    participant importer as FMI-importer
    participant client as client.dll
    participant server as server.exe
    participant dll as model.dll
    Note over importer,dll: Initialization
    importer->>client: fmi2Initialize
    client->>+server: spawn
    server->>-client: acknowledge
    client->>server:RPC_fmi2Initialize
    server->>dll: load
    server->>+dll: fmi2Initialize
    dll->>-server: fmi2Component (server_t *)
    server->>client: status
    client->>importer: fmi2Component (client_t*)
    Note over importer,dll: Main loop until fmi2FreeInstance
    importer->>+client: fmi2SetXXX
    client->>-importer: status
    importer->>+client: fmi2GetXXX
    client->>-importer: values
    importer->>client: fmi2DoStep
    client->>server: values
    client->>server: RPC_fmi2DoStep
    server->>+dll: fmiSetXXX
    server->>+dll: fmi2DoStep
    dll->>-server: status
    server->>+dll: fmiGetXXX
    server->>client: values
    server->>client: status
    client->>importer: status

Performances¶

To improve performance, this implementation minimize the number of Inter Process Communication calls. So that, values of signal of the DLL are cached on client side in local buffers.

How it's work ?¶

Considering win64 FMU, only the binaries/win64 folder is populated. It contains model.dll.

Add remoting win32: simulate 64bits FMU 32 bits OS¶

1. Copy client_sm.dll (32 bits) as model.dll in binaries/win32
2. Copy server_sm.exe (64 bits) in binaries/win64

When Simulation Enviroment will use the FMU on 32 bits OS: 1. it will load win32/model.dll (which is a copy of client_sm.dll) 2. which will communicate with win64/server_exe. 3. which will load win64/model.dll

Add remoting win64: simulate 32 bits FMU 64 bits OS¶

1. Copy client_sm.dll (64 bits) as model.dll in binaries/win64
2. Copy server_sm.exe (32 bits) in binaries/win32

When Simulation Enviroment will use the FMU on 64bits kernel: 1. it will load win64/model.dll (which is a copy of client_sm.dll) 2. which will communicate with win32/server_exe. 3. which will load win32/model.dll

Usage with fmutool¶

This feature is available easily with fmutool command line or with its graphical user interface: fmutool -input model64.fmu -add-remoting32 -output model64+32.fmu

LICENSE¶

Using the remoting code will alter your FMU by introducting additionnal interface. This code is released under the 2-Clause BSD license:

Copyright 2023-2025 Renault SAS

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS �AS IS� AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.