Building for Android NDK

If you have the ndk and prebuilt toolchains with that, you can simply build lws library for your android app from one cmake and one make command.

However if you want a tls lib, you have to take care of building and pointing to that first. But if it's a cmake project like mbedtls, that also is just a matter of one cmake and one make.

Installing NDK pieces

There's probably a more direct way but the official way is install the whole Android Studio and then run sdkmanager to install a recent NDK.

I installed the sdk and ndk pieces into /opt/android/ and that's how the ./contrib/cross-aarch64-android.cmake toolchain file is shipped. You can adapt some settings at the top of that file including the path if needed.

Fetching lws (needed first for cross toolchain file)

It doesn't care where you put these projects, but for simplicity they should be in the same parent dir, like

- /home/someone
 - /home/someone/libwebsockets
 - /home/someone/mbedtls

The reason is that building mbedtls need the cross toolchain file from libwebsockets, that's also why we have to get libwebsockets first now but build it later.

$ git clone https://libwebsockets.org/repo/libwebsockets

Building mbedtls

$ git clone https://github.com/ARMmbed/mbedtls.git
$ cd mbedtls
$ mkdir build
$ cd build
$ rm -f CMakeCache.txt && \
  cmake .. -DCMAKE_TOOLCHAIN_FILE=../libwebsockets/contrib/cross-aarch64-android.cmake \
  -DUSE_SHARED_MBEDTLS_LIBRARY=1 \
  -DENABLE_PROGRAMS=0 \
  -Wno-dev && \
  make -j && \
  cmake --install .

The lws toolchain file sets the path to install into as the cross root path, so despite it looks like the destination dir is missing for the install, it will go into, eg /opt/android/ndk/21.1.6352462/platforms/android-24/arch-arm64/lib/libmbedcrypto.a where lws will look for it

Building lws

You don't need to explain where mbedtls can be found... lws will build with the same toolchain file that sets the cross root to the same place as mbedtls, it will easily find them there without any further hints.

$ mkdir build
$ cd build
$ rm -f CMakeCache.txt && \
  cmake .. -DCMAKE_TOOLCHAIN_FILE=../libwebsockets/contrib/cross-aarch64-android.cmake \
  -DLWS_WITH_MBEDTLS=1 \
  -DLWS_WITHOUT_TESTAPPS=1 && \
  make && \
  cmake --install .

That's it, both mbedtls and lws library and header files are installed into the ndk cross root.