libwebsockets依赖libuv,libz,mbedtls，所以构建脚本需要提前构建以上几个库，下面介绍使用NDK的独立工具链（standalone toolchain）来编译步骤。独立工具链的参考链接为：https://developer.android.com/ndk/guides/standalone_toolchain

#!/bin/bash

# Build libwebsockets  library for Android

# path to NDK

export NDK=<Your_tool_path>/android-ndk-r17-beta2-linux-x86_64/android-ndk-r17-beta2

export ANDROID_NDK=${NDK}

export TOOLCHAIN=${NDK}/toolchain

export CORSS_SYSROOT=${NDK}/sysroot

export SYSROOT=${NDK}/platforms/android-22/arch-arm

set -e

# for zlib-1.2.8, libuv, mbedtls-2.11.0, libwebsockets-3.0

# create a local android toolchain

API=${3:-24}

$NDK/build/tools/make-standalone-toolchain.sh \

--toolchain=arm-linux-androideabi-4.9 \

--arch=arm \

--install-dir=`pwd`/android-toolchain-arm \

--platform=android-$API \

--stl=libc++ \

--force \

--verbose

# setup environment to use the gcc/ld from the android toolchain

export INSTALL_PATH=/media/luckfish/share_ext/libwebsockets_android/android-toolchain-arm

export TOOLCHAIN_PATH=`pwd`/android-toolchain-arm

export TOOL=arm-linux-androideabi

export NDK_TOOLCHAIN_BASENAME=${TOOLCHAIN_PATH}/bin/${TOOL}

export PATH=`pwd`/android-toolchain-arm/bin:$PATH

export CC=$NDK_TOOLCHAIN_BASENAME-gcc

export CXX=$NDK_TOOLCHAIN_BASENAME-g++

export LINK=${CXX}

export LD=$NDK_TOOLCHAIN_BASENAME-ld

export AR=$NDK_TOOLCHAIN_BASENAME-ar

export RANLIB=$NDK_TOOLCHAIN_BASENAME-ranlib

export STRIP=$NDK_TOOLCHAIN_BASENAME-strip

export PLATFORM=android

export CFLAGS="D__ANDROID_API__=$API"

# configure and build libuv

[ ! -f ./android-toolchain-arm/lib/libuv.so ] && {

cd libuv

echo "=============================================>> build libuv"

PATH=$TOOLCHAIN_PATH:$PATH make clean

PATH=$TOOLCHAIN_PATH:$PATH make

PATH=$TOOLCHAIN_PATH:$PATH make install

echo "<<============================================= build libuv"

cd ..

}

# configure and build zlib

[ ! -f ./android-toolchain-arm/lib/libz.a ] && {

cd zlib-1.2.8

echo "=============================================>> build libz"

PATH=$TOOLCHAIN_PATH:$PATH make clean

PATH=$TOOLCHAIN_PATH:$PATH make

PATH=$TOOLCHAIN_PATH:$PATH make install

echo "<<============================================= build libz"

cd ..

}

# configure and build mbedtls

[ ! -f ./android-toolchain-arm/lib/libmbedtls.so ] && {

echo "=============================================>> build mbedtls"

PREFIX=$TOOLCHAIN_PATH

cd mbedtls-2.11.0

[ ! -d build ] && mkdir build

cd build

export CFLAGS="$CFLAGS -fomit-frame-pointer"

PATH=$TOOLCHAIN_PATH:$PATH cmake .. -DCMAKE_TOOLCHAIN_FILE=`pwd`/../cross-arm-android-gnueabi.cmake \

  -DCMAKE_INSTALL_PREFIX:PATH=${INSTALL_PATH} \

  -DCMAKE_BUILD_TYPE=RELEASE -DUSE_SHARED_MBEDTLS_LIBRARY=On

PATH=$TOOLCHAIN_PATH:$PATH make clean

PATH=$TOOLCHAIN_PATH:$PATH make SHARED=1

PATH=$TOOLCHAIN_PATH:$PATH make install

echo "<<============================================= build mbedtls"

cd ../..

}

# configure and build libwebsockets

[ ! -f ./android-toolchain-arm/lib/libwebsockets.a ] && {

cd libwebsockets

[ ! -d build ] && mkdir build

cd build

echo "=============================================>> build libwebsockets"

PATH=$TOOLCHAIN_PATH:$PATH cmake .. -DCMAKE_TOOLCHAIN_FILE=`pwd`/../cross-arm-android-gnueabi.cmake \

  -DCMAKE_INSTALL_PREFIX:PATH=${INSTALL_PATH} \

  -DLWS_WITH_LWSWS=1 \

  -DLWS_WITH_MBEDTLS=1 \

  -DLWS_WITHOUT_TESTAPPS=1 \

  -DLWS_MBEDTLS_LIBRARIES="${INSTALL_PATH}/lib/libmbedcrypto.a;${INSTALL_PATH}/lib/libmbedtls.a;${INSTALL_PATH}/lib/libmbedx509.a" \

  -DLWS_MBEDTLS_INCLUDE_DIRS=${INSTALL_PATH}/include \

  -DLWS_LIBUV_LIBRARIES=${INSTALL_PATH}/lib/libuv.so \

  -DLWS_LIBUV_INCLUDE_DIRS=${INSTALL_PATH}/include \

  -DLWS_ZLIB_LIBRARIES=${INSTALL_PATH}/lib/libz.so \

  -DLWS_ZLIB_INCLUDE_DIRS=${INSTALL_PATH}/include

PATH=$TOOLCHAIN_PATH:$PATH make

PATH=$TOOLCHAIN_PATH:$PATH make install

echo "<<============================================= build libwebsockets"

cd ../..

}

后记：

如果单独编译mbedtls库，可以使用命令：

1）cmake .. -DCMAKE_TOOLCHAIN_FILE=`pwd`/../cross-arm-android-gnueabi.cmake -DCMAKE_BUILD_TYPE=RELEASE -DUSE_SHARED_MBEDTLS_LIBRARY=On

2）删除build目录下的CMakeCache.txt

3）cmake -DUSE_SHARED_MBEDTLS_LIBRARY=On ..

4）make

得到动态库，其中cross-arm-android-gnueabi.cmake 指定了编译工具，

cross-arm-android-gnueabi.cmake文件如下：

#

# CMake Toolchain file for crosscompiling on ARM.

#

# This can be used when running cmake in the following way:

#  cd build/

#  cmake .. -DCMAKE_TOOLCHAIN_FILE=../cross-arm-linux-gnueabihf.cmake

#

set(CROSS_PATH /media/xxx/share_ext/libwebsockets_android/android-toolchain-arm)

# Target operating system name.

set(CMAKE_SYSTEM_NAME Android)

# Target build dynamic libs.

set(BUILD_SHARED_LIBS ON)

# Name of C compiler.

set(CMAKE_C_COMPILER "${CROSS_PATH}/bin/arm-linux-androideabi-gcc")

set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-androideabi-g++")

# Where to look for the target environment. (More paths can be added here)

set(CMAKE_FIND_ROOT_PATH "${CROSS_PATH}")

# Adjust the default behavior of the FIND_XXX() commands:

# search programs in the host environment only.

set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)

# Search headers and libraries in the target environment only.

set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)

set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)