Host Emulator

The latest versions of Sming allow most of components of the library and the sample applications to be compiled on a Linux/Windows host system and be tested before uploading them to the microcontroller.

If you want to try it we have an interactive tutorial that can be run directly from your browser.

See Getting Started for installation details.

The following sections provide more background detail.

Requirements (Linux)

Modern Linux distribution

Most popular modern distributions should be fine. At the moment we develop only with Ubuntu 16.04 and 18.04.

C/C++ 32 bit compiler and libraries

The latest versions of Sming require GCC version 8 or newer. If your OS is 64 bit then 32 bit C/C++ compiler and libraries are also required. Here’s a summary of how to do this:

sudo apt update
sudo apt install gcc-9 g++-9

# For 64-bit systems
sudo apt install gcc-9-multilib g++-9-multilib

# Set GCC 9 as default
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 60 --slave /usr/bin/g++ g++ /usr/bin/g++-9

The current version is GCC 9.3.0.

CMake 3.8 or newer

For the compilation of LWIP CMake version 3.8 or newer is required. In order to get newer CMake version under Ubuntu 16.04, do this:

cd /tmp
sudo mkdir /opt/cmake
sudo sh --prefix=/opt/cmake
sudo mv /usr/bin/cmake /usr/bin/cmake.orig
sudo ln -s /opt/cmake/bin/cmake /usr/bin/cmake

Requirements (Windows)

For Windows, make sure your MinGW distro is up to date. The current version is GCC 8.2.0.


If you don’t already have MinGW installed, see Windows Installation.


Environment variables

SMING_ARCH must be set to use Host as the desired architecture:

export SMING_ARCH=Host

Debug Build

If you plan to use a debugger make sure to set ENABLE_GDB and (optionally) ENABLE_LWIPDEBUG before compiling the code:

export ENABLE_GDB=1
export ENABLE_LWIPDEBUG=1  # <!-- this will compile also LWIP with debug symbols

Initial Clean-up

Make sure that you are working on a clean source code tree. The following commands may help:

make dist-clean

Sample compilation

Compile a sample as usual:

cd $SMING_HOME/../samples/Basic_Blink

Adapting existing code

You may need to modify your existing applications to work with the emulator. Architecture-specific code should be moved into separate code modules. Code that is specific to the ESP8266 may be conditionally compiled using #ifdef ARCH_ESP8266. Similarly, you can check if the code is compiled for the emulator using #ifdef ARCH_HOST.

Running on the host

Once the sample is compiled, initialise the Virtual Flasher:

make flash

If enabled, this will also create a SPIFFS file system and write it to flash.

To run the application, do this:

make run


Support is provided via TAP network interface (a virtual network layer operating at the ethernet frame level). A TAP interface must be created first, and requires root privilege. You can use the Sming/Arch/Host/Tools/ Here is the manual approach:

sudo ip tuntap add dev tap0 mode tap user `whoami`
sudo ip a a dev tap0
sudo ip link set tap0 up

# The following lines are needed if you plan to access Internet
sudo sysctl net.ipv4.ip_forward=1
sudo sysctl net.ipv6.conf.default.forwarding=1
sudo sysctl net.ipv6.conf.all.forwarding=1

export INTERNET_IF=wlan0 # <!--- Make sure to replace wlan0 with the network interface connected to Internet

sudo iptables -t nat -A POSTROUTING -o $INTERNET_IF -j MASQUERADE
sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i tap0 -o $INTERNET_IF -j ACCEPT

This creates the tap0 interface. The emulator will automatically select the first tap interface found. To override this, use the --ifname option.

You can list available network interfaces thus:

ip link


Issue 1: fatal error: sys/cdefs.h: No such file or directory

Make sure to install the 32bit version of the GNU C and C++ compiler, development package and libraries.

Issue 2: fatal error: bits/c++config.h: No such file or directory

Make sure to install the 32bit version of the GNU C and C++ compiler, development package and libraries.

Further reading