Introduction
------------
Libwebsockets can be built using two different build systems
autoconf or CMake. autoconf only works on Unix systems, or mingw/cygwin
on Windows. CMake works differently and can generate platform specific
project files for most popular IDEs and build systems.

################################### Autoconf ###################################

Building the library and test apps
----------------------------------

You need to regenerate the autotools and libtoolize stuff for your system

$ ./autogen.sh


------Fedora x86_64

 ./configure --prefix=/usr --libdir=/usr/lib64 --enable-openssl

------Apple

Christopher Baker reported that this is needed
(and I was told separately enabling openssl makes trouble somehow)

./configure CC="gcc -arch i386 -arch x86_64" CXX="g++ -arch i386 -arch
x86_64" CPP="gcc -E" CXXCPP="g++ -E" --enable-nofork

------mingw

I did the following to get working build, ping test is disabled when
building this way

1) install mingw64_w32 compiler packages from Fedora
2) additionally install mingw64-zlib package
3) ./configure --prefix=/usr --enable-mingw --host=x86_64-w64-mingw32
4) make

------MIPS cross-build using OpenWRT

 ./configure --prefix=/usr --without-extensions --host mips-openwrt-linux

I did not try building the extensions since they need cross-zlib, but it
should also be workable.

------Other uClibc

you may need --enable-builtin-getifaddrs if your toolchain
doesn't have it - openWRT uclibc has it so you don't need this option.

------ARM cross-build

./configure --prefix=/usr --host=arm-linux-gnueabi --without-client --without-extensions

you can build cross with client and extensions perfectly well, but
apart from the size shrink this has the nice characteristic that no
non-toolchain libraries are needed to build it.


otherwise if /usr/local/... and /usr/local/lib are OK then...

$ ./configure
$ make clean
$ make && sudo make install
$ libwebsockets-test-server

should be enough to get a test server listening on port 7861.


Configure script options
------------------------

There are several other possible configure options

--enable-openssl	Builds in the SSL support

--with-cyassl		Use cyassl instead of OpenSSL... you will need CyaSSL
			to have been configured with --enable-opensslExtra
\			when it was built.

--enable-libcrypto	by default libwebsockets uses its own
			built-in md5 and sha-1 implementation for
			simplicity.  However the libcrypto ones
			may be faster, and in a distro context it
			may be highly desirable to use a common
			library implementation for ease of security
			upgrades.  Give this configure option
			to disable the built-in ones and force use
			of the libcrypto (part of openssl) ones.

--with-client-cert-dir=dir   tells the client ssl support where to
			     look for trust certificates to validate
			     the remote certificate against.

--enable-noping		Don't try to build the ping test app
			It needs some unixy environment that
			may choke in other build contexts, this
			lets you cleanly stop it being built
			
--enable-builtin-getifaddrs  if your libc lacks getifaddrs, you can build an
			implementation into the library.  By default your libc
			one is used.

--without-testapps	Just build the library not the test apps

--without-client	Don't build the client part of the library nor the
			test apps that need the client part.  Useful to
			minimize library footprint for embedded server-only
			case

--without-server	Don't build the server part of the library nor the
			test apps that need the server part.  Useful to
			minimize library footprint for embedded client-only
			case

--without-daemonize	Don't build daemonize.c / lws_daemonize

--disable-debug		Remove all debug logging below lwsl_notice in severity
			from the code -- it's not just defeated from logging
			but removed from compilation

--without-extensions	Remove all code and data around protocol extensions.
			This reduces the code footprint considerably but
			you will lose extension features like compression.
			However that may be irrelevant for embedded use and
			the code / data size / speed improvements may be
			critical.

--with-latency		Builds the latency-tracking code into the library...
			this slows your library down a bit but is very useful
			to find the cause of unexpected latencies occurring
			inside the library.  See README.test-apps for more
			info


Externally configurable important constants
-------------------------------------------

You can control these from configure by just setting them as commandline
args throgh CFLAGS, eg

./configure CFLAGS="-DLWS_MAX_ZLIB_CONN_BUFFER=8192"


They all have reasonable defaults usable for all use-cases except resource-
constrained, so you only need to take care about them if you want to tune them
to the amount of memory available.

 - LWS_MAX_HEADER_NAME_LENGTH default 64: max characters in an HTTP header
name that libwebsockets can cope with

 - LWS_MAX_HEADER_LEN default 4096: largest HTTP header value string length
libwebsockets can cope with

 - LWS_INITIAL_HDR_ALLOC default 256: amount of memory to allocate initially,
tradeoff between taking too much and needless realloc

 - LWS_ADDITIONAL_HDR_ALLOC default 64: how much to additionally realloc if
the header value string keeps coming

 - LWS_MAX_PROTOCOLS default 10: largest amount of different protocols the
server can serve

 - LWS_MAX_EXTENSIONS_ACTIVE default 10: largest amount of extensions we can
choose to have active on one connection

 - SPEC_LATEST_SUPPORTED default 13: only change if you want to remove support
for later protocol versions... unlikely

 - AWAITING_TIMEOUT default 5: after this many seconds without a response, the
server will hang up on the client

 - CIPHERS_LIST_STRING default "DEFAULT": SSL Cipher selection.  It's advisable
to tweak the ciphers allowed to be negotiated on secure connections for
performance reasons, otherwise a slow algorithm may be selected by the two
endpoints and the server could expend most of its time just encrypting and
decrypting data, severely limiting the amount of messages it will be able to
handle per second.  For example::

    "RC4-MD5:RC4-SHA:AES128-SHA:AES256-SHA:HIGH:!DSS:!aNULL"

 - SYSTEM_RANDOM_FILEPATH default "/dev/urandom": if your random device differs
you can set it here

 - LWS_MAX_ZLIB_CONN_BUFFER  maximum size a compression buffer is allowed to
grow to before closing the connection.  Some limit is needed or any connecton
can exhaust all server memory by sending it 4G buffers full of zeros which the
server is expect to expand atomically.  Default is 64KBytes.

 - LWS_SOMAXCONN  maximum number of pending connect requests the listening
socket can cope with.  Default is SOMAXCONN.  If you need to use synthetic
tests that just spam hundreds of connect requests at once without dropping
any, you can try messing with these as well as ulimit (see later)
(courtesy Edwin van der Oetelaar)

echo "2048 64512" > /proc/sys/net/ipv4/ip_local_port_range
echo "1" > /proc/sys/net/ipv4/tcp_tw_recycle
echo "1" > /proc/sys/net/ipv4/tcp_tw_reuse
echo "10" > /proc/sys/net/ipv4/tcp_fin_timeout
echo "65536" > /proc/sys/net/core/somaxconn
echo "65536" > /proc/sys/net/ipv4/tcp_max_syn_backlog
echo "262144" > /proc/sys/net/netfilter/nf_conntrack_max


Memory efficiency
-----------------

Update at 35f332bb46464feb87eb

Embedded server-only configuration without extensions (ie, no compression
on websocket connections), but with full v13 websocket features and http
server, built on ARM Cortex-A9:

./configure --without-client --without-extensions --disable-debug --enable-nofork --without-daemonize

.text	.rodata	.data	.bss
11476	2664	288	4

Context Creation, 1024 fd limit[2]: 12288 (12 bytes per fd)
Per-connection [3]: 4400 bytes


This shows the impact of the major configuration with/without options at
13ba5bbc633ea962d46d using Ubuntu ARM on a PandaBoard ES.

These are accounting for static allocations from the library elf, there are
additional dynamic allocations via malloc

Static allocations, ARM9
				.text	.rodata	.data	.bss
 All (no without)		35024	9940	336	4104
 without client			25684	7144	336	4104
 without client, exts		21652	6288	288	4104
 without client, exts, debug[1]	19756	3768	288	4104
 without server			30304	8160	336	4104
 without server, exts		25382	7204	288	4104
 without server, exts, debug[1]	23712	4256	288	4104

Dynamic allocations: ARM9 (32 bit)

 Context Creation, 1024 fd limit[2] in ulimit:	12288  (12 bytes per fd)
 Per-connection (excluding headers[3]):		 8740

Dynamic allocations: x86_64 (64 bit)

 Context Creation, 1024 fd limit[2] in ulimit:	16384  (16 bytes per fd)
 Per-connection (excluding headers[3]):		 9224

[1] --disable-debug only removes messages below lwsl_notice.  Since that is
the default logging level the impact is not noticable, error, warn and notice
logs are all still there.

[2] 1024 fd per process is the default limit (set by ulimit) in at least Fedora
and Ubuntu.

[3] known headers are retained via additional mallocs for the lifetime of the
connection


#################################### CMake ####################################

CMake is a multi-platform build tool that can generate build files for many
different target platforms. See more info at http://www.cmake.org

CMake also allows/recommends you to do "out of source"-builds, that is, 
the build files are separated from your sources, so there is no need to 
create elaborate clean scripts to get a clean source tree, instead you 
simply remove your build directory.

Libwebsockets has been tested to build successfully on the following platforms
with SSL support (both OpenSSL/CyaSSL):

- Windows
- Linux (x86 and ARM)
- OSX
- NetBSD

Building the library and test apps
----------------------------------

The project settings used by CMake to generate the platform specific build
files is called CMakeLists.txt. CMake then uses one of its "Generators" to
output a Visual Studio project or Make file for instance. To see a list of
the available generators for your platform, simply run the "cmake" command.

Note that by default OpenSSL will be linked, if you don't want SSL support
see below on how to toggle compile options.

Building on Unix:
-----------------

1. Install CMake 2.6 or greater: http://cmake.org/cmake/resources/software.html
   (Most Unix distributions comes with a packaged version also)

2. Install OpenSSL.

3. Generate the build files (default is Make files):

	cd /path/to/src
	mkdir build
	cd build
	cmake ..

	(NOTE: The build/ directory can have any name and be located anywhere
	 on your filesystem, and that the argument ".." given to cmake is simply
	 the source directory of libwebsockets containing the CMakeLists.txt project
	 file. All examples in this file assumes you use "..")

4. Finally you can build using the generated Makefile:

	make

Building on Windows (Visual Studio)
-----------------------------------
1. Install CMake 2.6 or greater: http://cmake.org/cmake/resources/software.html

2. Install OpenSSL binaries. http://www.openssl.org/related/binaries.html
   (Preferably in the default location to make it easier for CMake to find them)

3. Generate the Visual studio project by opening the Visual Studio cmd prompt:

   cd <path to src>
   md build
   cd build
   cmake -G "Visual Studio 10" ..

   (NOTE: There is also a cmake-gui available on Windows if you prefer that)

4. Now you should have a generated Visual Studio Solution in  your
   <path to src>/build directory, which can be used to build.

Setting compile options
-----------------------

To set compile time flags you can either use one of the CMake gui applications
or do it via command line.

Command line
------------
To list avaialable options (ommit the H if you don't want the help text):

	cmake -LH ..

Then to set an option and build (for example turn off SSL support):

	cmake -DWITH_SSL=0 ..
or
	cmake -DWITH_SSL:BOOL=OFF ..

Unix GUI
--------
If you have a curses enabled build you simply type:
(not all packages include this, my debian install does not for example).
	
	ccmake

Windows GUI
-----------
On windows CMake comes with a gui application:
	Start -> Programs -> CMake -> CMake (cmake-gui)

CyaSSL replacement for OpenSSL
------------------------------
CyaSSL is a lightweight SSL library targeted at embedded system:
http://www.yassl.com/yaSSL/Products-cyassl.html

It contains a OpenSSL compatability layer which makes it possible to pretty
much link to it instead of OpenSSL, giving a much smaller footprint.

NOTE: At the time of writing this the current release of CyaSSL contains a 
crash bug due to some APIs libwebsocket uses. To be able to use this you will
need to use the current HEAD in their official repository:
	https://github.com/cyassl/cyassl

NOTE: cyassl needs to be compiled using the --enable-opensslExtra flag for
this to work.

Compiling libwebsockets with CyaSSL
-----------------------------------

cmake -DUSE_CYASSL=1 
	  -DCYASSL_INCLUDE_DIRS=/path/to/cyassl 
	  -DCYASSL_LIB=/path/to/cyassl/cyassl.a ..

NOTE: On windows use the .lib file extension for CYASSL_LIB instead.

Cross compiling
---------------
To enable cross compiling libwebsockets using CMake you need to create
a "Toolchain file" that you supply to CMake when generating your build files.
CMake will then use the cross compilers and build paths specified in this file
to look for dependencies and such.

Below is an example of how one of these files might look like:

	#
	# CMake Toolchain file for crosscompiling on ARM.
	#
	# This can be used when running cmake in the following way:
	#  cd build/
	#  cmake .. -DCMAKE_TOOLCHAIN_FILE=/path/to/this/file/TC_arm-linux-gcc.cmake
	#

	set(CROSS_PATH /path/to/cross_environment/uClibc)

	# Target operating system name.
	set(CMAKE_SYSTEM_NAME Linux)

	# Name of C compiler.
	set(CMAKE_C_COMPILER "${CROSS_PATH}/bin/arm-linux-uclibc-gcc")
	set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-uclibc-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)

Additional information on cross compilation with CMake:
	http://www.vtk.org/Wiki/CMake_Cross_Compiling