Part 1: Multiplayer WebSocket Game server written in C using libuv & libwebsockets & Cocos2d-x-HTML5

The motivation to write this 6 part set of tutorials is to show developers how to build fast websockets game server Written in C using open source frameworks . and Cocos2d-x the HTML5 version for the  game client.

This tutorial is only to get your feet wet in this huge field of real time game servers .
It is real simple and teach you how to make single action , that is
moving players on all clients in real time .
also there are parts which are not finished yet like GEM"S on screen , ignore them for now.

This is the end result :

You can check the source code here :
https://github.com/meiry/Tutorial_mmo_websocket_game_server_c_libuv_libwebsockets_Cocos2d-x-HTML5

I'm quite aware of the huge hype using servers like Node.js for such tasks.or even Java Netty 
Especially when choosing event based a sync single thread server .
Although they are great servers and they are proven to be robust they have bottlenecks. for example:
(Notice those are very high level claims based on my own almost 20 years of development experience ).

Node.js using V8 engine as its JavaScript interpreter which originally designed for the chrome browser. huge frameworks are written in pure JavaScript which this browser interpreter needs to chew.

Java Netty is using the java JVM which it is a Software that execute your java Software in memory or not still.The JVM do take extra server resources despite the JVM have its own fine tuning configurations the results on very high load are sometimes unexpected . and of course the GC.

Therefore I want to present option which is not so popular BUT it will  probably utilize your physical server the most. and as result will save you money. 
see games like Agar.io or slither.io their server build using c++ .

The tutorials are written to show you the basic usage of client/server connectivity , don't expect to see full blown game made . this is just a demo .
I will use the Authoritative server model and Client side prediction , to read more about it please
Please Refer to this great theoretical explanation about this model:
http://www.gabrielgambetta.com/fpm1.html
Written by Gabriel Gambetta .

The server and client is build on top and with the help of those great open source cross platform libraries:

1. Libuv  v1.90: this is the Node.js network library which abstracts the network event based model.
2. libwebsockets  v2.0: cross platform C web sockets library
3. list, hashmap , array files from android-system-core : C helpers  
4. cJSON : fast c json writer/reader
5. Cocos2d-x HTML5 : game engine. 

The project is developed in windows using Visual Studio  2013 c++  for the server.
And Chrome browser for the client .
Latter on i will add Linux and Mac support all code is cross platform .

Lets start with downloading libuv and libwebsockets and configuring them for compilation then compiling the server frameworks , after that we will learn the game server logic. and build simple client.

1. Libuv compilation.
Download libuv from the link below or git clone the master repository from here :
https://github.com/libuv/libuv
Then open the VS2013 x86 Native Tools Command Prompt  which located in the visual studio 2013
Tools directory .
browse to the libuv root directory and execute the vcbuild.bat :

After its done , it will create the VS Sulotion file in the root dir , open VS and load uv.sln
Then befor compiling go to Libuv -> right click -> properties -> C/C++ -> Code Generation
And chnage it to /MDd



Compile !
It create the libuv.lib file located in :
libuv\libuv-1.x\libuv-1.x\Debug\lib\libuv.lib
2. Libwebsockets compilation.
Download libwebsockets from the link below or git clone the master repository from here :
https://github.com/warmcat/libwebsockets

To configure and create the VS Solution files we will use CMAKE GUI tools , im using v3.5
Open cmake gui and point to the libwebsockets root directory .
And to the build directory where cmake will create the VS build files.
Click the configure button to revile the Cmake variables we need to feel .
It will open popup window there chose Visual Studio 2013



After the first configuration interation it will popup error window this is becose there few things we need to configure so libwebsockets work with libuv.
In the main cmake gui where its all painted in red do as follow : set the proper values

LWS_WITH_LIBUV    checked
LWS_WITH_STATIC   checked
LWS_WITH_SSL         un checked
LWS_LIB_INCLUDE_DIRS = d:\dev\cpp\gamedevcraft\libuv\libuv-1.x\libuv-1.x\include
LWS_LIBUV_LIBRARIES   = d:\dev\cpp\gamedevcraft\libuv\libuv-1.x\libuv-1.x\Debug\lib\libuv.lib

Click again configure , you should see the massage : Configuration Done .

Click the Generate button , the massage : Generate done  should appear .



Now go to the build directory and load the libwebsockets.sln solution file into VS 2013.
We only need to compile websockets project . so compile it .
The product will be static libwebsokctes file : websockets_static.lib this is the file we are going to use together with libuv compiled statically to our main server application .

3.Creating the VS project for our server.

First Download the source code of the game server from this GitHub repository :
https://github.com/meiry/Tutorial_mmo_websocket_game_server_c_libuv_libwebsockets_Cocos2d-x-HTML5
These files are the logic of the game server .
In VS go to :
Open -> New Project ->Visual C++ -> Win32 Console Application ,

At the button in the same window give the project name :

I called it "libuv_libwebsocket_cocos2dx_server" , and set directory for the project.
Then press Ok .
In the Next window click the the Next button
In the third window Uncheck the "Precompiled header" and click "Finish".
Now that you created the project lets import the source files and configure the project .
Copy the files which downloaded from GitHub and copy them to the root of the new created project.
Create new directory called libs  also in the root directory
Into the libs directory copy the libraries we compiled in the previous steps (1 & 2) :
libuv.lib , websockets_static.lib , zlib_internal.lib

sources :

libs:



We now going to add all those libs + headers + sources files into our VS project .
Right click on the "Header Files" in the new created project in VS  go to :
Add -> Existing item
Browse to the new created project root directory  and select all the headers there



Do the same but now right click on the source directory in VS under the new project and add the C files :



You need also include the cJSON c file , so repeat the same process for the files: cJSON_Utils.c cJSON.c


Project configuration :
Right click on the project go to :

C/C++ -> General -> Additional include Directories :  add the headers path
include;include\uv;include\lws;include\lws\win32helpers\;include\cjson;





Then go to:
C/C++ ->  Preprocessor -> Preprocessor definitions

Verify you have those set :
WIN32
_DEBUG
_WINDOWS
_CONSOLE
_LIB
_CRT_SECURE_NO_DEPRECATE
_CRT_NONSTDC_NO_DEPRECATE

Then go to:

C/C++ -> Code generation -> Runtime library 

And verify it set to (/MDd) 


Then go to :
Linker -> General -> Additional Library Directories And add the libs directory we created in the previous step




Then go to :
Linker -> Input -> additional dependencies
And verify you have those library names ( this part will be different in Linux configuration )

advapi32.lib
iphlpapi.lib
psapi.lib
userenv.lib
ws2_32.lib
libuv.lib
websockets_static.lib

zlib_internal.lib

Then go to :
Linker ->SubSystem 
verify it set to  : Console (/SUBSYSTEM:CONSOLE)

That's all ! compile the project
You should see  build\Debug\libuv_libwebsocket_cocos2dx_server.exe  file create.

Go to PART 2 where we dive into the server source code