Preparation of TSP-CSC5061

For TSP-CSC5061, we recommend that you install Visual Studio IDE on your personal computer (running a native Windows or a Windows on a virtual machine because:

• The linter (family of tools designed to statically analyze source code) SonarLint can be easily integrated to Visual Studio, but not CLion which we mention afterwards.
• It will ease our support in case of compilation/linking problems.
• This IDE is widely used in video games industry. Knowing a little bit this IDE can be an advantage.

Notes:

1. We rely on Visual Studio 2019. If you have a previous version of Visual Studio, this could mean you use a previous version of the compiler and the linker. This could lead to link problems when we will use Photon library. If you have the possibility, install Visual Studio 2019.
2. As we are conscious the some of you may dislike Microsoft, we also support CLion IDE.
3. If you use another IDE (in particular Visual Studio Code), we are not sure to make a good support for you.

We propose that you install Visual Studio Community because it is free. Now, if you have access to a free programm to get Visual Studio Enterprise, do not hesitate to take advantage of it (We think its interface is a bit nicer).

We do not recommend the use of Visual Studio Code as it is less powerfull than Visual Studio and CLion. Ina addition, our support will be very low. Nevertheless, here are the information for installing it :

• Install cmake from https://cmake.org/
• Download the installer from https://code.visualstudio.com, install it and lauch it.
• In https://code.visualstudio.com, click on Extensions. Then, find C/C++ extension and install it. Once the extension window appears in Visual Studio Code, click on button "Install"
• Install also "CMake" and "CMake Tools" extensions.

• Get ISO of Ubuntu Desktop 20.04.1 or Xubuntu 20.04 LTS
• Install VirtualBox.

Create a new virtual machine :

• Resource parameters have an influence on the performance of your VM. Recommended values 2GB RAM, 2 CPUs, 128 Mo Video RAM, 3D acceleration.
• Once the VM is created, "mount" the ISO in the virtual and start the VM.
• Follow Ubuntu installation steps.
• You will be asked to create a user account (during the labs, we will speak about ubuntu_user) and a password (for conveniency, you should chosse a simple one).
• Check that you can access Internet from your virtual machine: For instance, open a web page from a browser.

By default, copy-paste between host computer (the one running VirtualBox) and guest computer (the one running inside VirtualBox is deactivated. To activate it, in the window enclosing your guest machine: Menu Devices > Shared copy-paste > Bidirectional

VirtualBox Guest Additions is a set of tools which can be installed on your VM to ease its run.

• In your virtual machine, open a terminal and type the following commands:

sudo apt-get install -y build-essential module-assistant gcc make perl dkms
sudo m-a prepare

• In the window enclosing your guest machine: Menu Devices > Insert Guest Additions CD image...
• Follow installation instructions in the VM (Note: if you are using Xubuntu, open a terminal and type command sudo /media/simatic/VBox_GAs_5.2.18/VBoxLinuxAdditions.run)
• In a VM terminal: sudo usermod -a -G vboxsf $USER
• Shutdown the VM.
• In VM parameters in VirtualBox, add a shared directory which points on the root of Visual Studio projects on which you working.
• NOTE: Tick option "Automatic mount".
• Start the VM.
• In VM file explorer, your directory must be visible. Note: In a terminal, your shared directory is a subdirectory of /media directory.
• Check that writing a file and reading a file are possible from the VM (Ubuntu) as well as the host (Windows).

• Uncompress Client_Server_CPP.zip in the directory you prefer.
• Apply cmake procedure of this document. You should obtain 6 executables.

We will run the application to better understand it:

• Six executables were generated by cmake procedure:
  • tsp_ClientMonoThread.exe, tcp_ClientMultiThread.exe and tcp_serverMultiThread.exe on which we will concentrate in this section.
  • udp_ClientMonoThread.exe, udp_ClientMultiThread.exe and udp_server.exe which we will use later (but, if you want, you can take a look at the sources).

• Start multithreaded server with Debug > Execute without debugging: A Windows security alert window related to the firewall may open (see next figure). Tick all checkbox (to authorize your server in whatever network circumstances) and chick on button "Authorize access": The terminal of the server appears.

  

  Figure 4: Window "Windows security alert" related to firewall

• Then, start multithreaded client. Here are commented logs:

# "S:" = Serveur ; "C:" = Client
S: Waiting for connections on port 4096 # Server waits that clients connect to port 4096
   C: My clientName is 'host=PAT13450/pid=42040'
   C: Connect to localhost:4096 # Client tries to connect to local server, on port 4096
                                # Once connection is established, client request its clientId
S: Client '0' is connected and requesting its clientId # Server accepted connection from client and clientId request: It answers.
   C: Received my clientId from server. It is '0' # Client receives its clientId from server.
   C: Broadcasting 60 messages (at frequency of 1 message per second)
   C: Request to broadcast integer: 1 # Client requests the server to broadcast integer value 1 to all clients connected to server.
S: Client '0' requests to broadcast int "1" # Server receives request and handles it.
   C: Client '0' has broadcast (thanks to server) integer: 1 # Client receives broadcast from server.
#
# Etc.
#
   C: Request to broadcast integer: 60
S: Client '0' requests to broadcast int "60"
   C: Client '0' has broadcast (thanks to server) integer: 60
   C: Done # As client has sent the 60 messages it wanted to send, it stops.
S: Client '0' disconnected # Server detects client disconnection.

Now, launch in parallel the exection of two simultaneous multithreaded clients in parallel. Observe that messages are received in the same order by both clients.

Analyze source code of tcp_serverMultiThread.cpp and tcp_clientMultiThread.cpp (do not care about tcp_clientMonoThread.cpp ; we will focus on it in next section). Check that you understand:

1. why server is multithreaded,
2. what's the use of mutexVec variable in the server,
3. why vecClientSock and mutexVec variables are defined as static,
4. why client is multithreaded.

Note: Method sf::TcpListener::listen() relies on bind() and listen() system calls which are classically used by network programmers.

Question to challenge your understanding of this programs. Suppose that, during the same execution of the server, different clients connect to the server, request it to send broadcast messages, and then disconnect. Is it possible that several clients receive the same clientId? If you are not able to give an answer or to explain why, do not hesitate to ask on discord.

Other question (No need to implement): How to modify the server in order to guarantee that no client will ever have the same clientId than a previous client (except if there are more than 2 billions clients)?

tcp_clientMonoThread.cpp contains the code of a monothread client. This code will be useful when coding our homemade middleware MyPhoton". You can study it directly to understand how it worls. But you can take the more challenging path:

1. Copy tsp_clientMultiThread.cpp to tcp_clientMonoThread.cpp
2. Read tutorial on non-blocking sockets.
3. Modify tcp_clientMonoThread.cpp so that:
   1. Reading on socket is non-blocking;
   2. Each time you write on the socket, check whether there is a packet to raead or not. If it is, read it and process it. Then check whether there is another packet waiting;
   3. Writing on socket takes into account that socket is non-blocking;
   4. You sleep 1000 millisecondes before sending another packet.
4. Check your client works properly with the server.

By turning our server into a mono-thread server, we get rid of synchronization problems. In other words, we do not need mutexVec any more.

Read tutorial "Blocking on a group of sockets" and code example present in documentation of class sf::SocketSelector: You should be able to write tcp_serverMonoThread.cpp, a mono-threaded version of the TCP server.

TODO: Source code of mono-threaded version of the server.