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75. Multiplayer

This explains the basic steps to create multiplayer games using the Photon SDK.

75.1 Photon SDK Setup

75.1.1 Downloading Photon SDK

  1. Download the Photon Realtime SDK (compressed in 7z format) for your development environment. The SDK version verified with Siv3D v0.6.16 is v5.0.12
  2. Extract the downloaded file and place it in an appropriate location (you'll set include/library paths to this folder path in the following steps, so don't move it afterward)

75.1.2 Preparing Siv3D Project

  1. Create a Siv3D application project as usual
  2. Copy three files Multiplayer_Photon.hpp, Multiplayer_Photon.cpp, PHOTON_APP_ID.SECRET from the Addon/Multiplayer_Photon folder within the Siv3D SDK folder* to the folder containing Main.cpp in your project
  3. To use the Multiplayer_Photon library in your project, add the copied Multiplayer_Photon.hpp and Multiplayer_Photon.cpp to your project and include them in the build target. However, this will fail to build as include/library paths to the Photon SDK are not set yet
  4. (For Windows) In project settings, add the downloaded Photon SDK folder path (e.g., C:/Users/siv3d/Desktop/libs/Photon-Windows-Sdk_v5-0-12-0s) to both Include Directories and Library Directories
  5. (For macOS) In project settings, add the downloaded Photon SDK folder path to Header Search Paths in Build Settings, add 4 paths ●●●/Common-cpp/lib, ●●●/LoadBalancing-cpp/lib, ●●●/Photon-cpp/lib, ●●●/3rdparty/lib/apple to Library Search Paths (●●● is the Photon SDK folder path), then add 4 files libCommon-cpp_release_macosx.a, libLoadBalancing-cpp_release_macosx.a, libPhoton-cpp_release_macosx.a, libcrypto_release_macosx.a from those folders to Link Binary With Libraries in Build Phases
  6. If you can build successfully, project setup is complete

Siv3D SDK Folder

  • This is the folder created when you install Siv3D
    • For macOS, this is the downloaded Siv3D SDK itself
    • For Windows, it's created by default in the Documents folder with the name OpenSiv3D_0.6.*

75.1.3 Setting Photon App ID

  1. After logging into the Photon website, open the dashboard screen
  2. Press CREATE A NEW APP on the dashboard screen, enter the information, and press CREATE to issue a new Photon App ID. Select Realtime for Photon Type. Other input items are optional
  3. The issued Photon App ID is a random alphanumeric string like "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
  4. Replace the placeholder App ID "00000000-0000-0000-0000-000000000000" written in PHOTON_APP_ID.SECRET added to your project in 75.1.2 with the issued Photon App ID
  5. (If managing the project with git) This Photon App ID must not be known by third parties. Use .gitignore to exclude PHOTON_APP_ID.SECRET from management

75.2 First Program

Include

  • Include "Multiplayer_Photon.hpp" and "PHOTON_APP_ID.SECRET" after <Siv3D.hpp>.

Inheriting Multiplayer_Photon

  • Create a class MyNetwork (name is arbitrary) that inherits from Multiplayer_Photon, and inherit Multiplayer_Photon's constructor with using Multiplayer_Photon::Multiplayer_Photon;.

Storing Photon App ID

  • Use const std::string secretAppID{ SIV3D_OBFUSCATE(PHOTON_APP_ID) }; to store the Photon App ID in secretAppID at runtime
  • Directly using const std::string secretAppID{ PHOTON_APP_ID }; would expose the Photon App ID as-is when analyzing the binary of the built executable, but wrapping it with SIV3D_OBFUSCATE() provides some obfuscation

Creating MyNetwork

  • Create a MyNetwork object. Pass three parameters to the constructor: Photon App ID, application version, and whether to enable detailed debug display
  • Even with the same Photon App ID, programs with different application versions cannot communicate. This prevents communication between old and new versions after game version updates
  • Enabling detailed debug display (Verbose::Yes) sets the protected member variable m_verbose of the Multiplayer_Photon class to true, and when various callback functions of Multiplayer_Photon are called, detailed information is output via Print
    • This is useful for debugging during development. Choose Verbose::No for release to turn off output
# include <Siv3D.hpp>
# include "Multiplayer_Photon.hpp"
# include "PHOTON_APP_ID.SECRET"

// Class inheriting from Multiplayer_Photon
class MyNetwork : public Multiplayer_Photon
{
public:

	// Inherit Multiplayer_Photon constructor
	using Multiplayer_Photon::Multiplayer_Photon;
};

void Main()
{
	// Resize window to 1280x720
	Window::Resize(1280, 720);

	// Photon App ID
	// Wrap with SIV3D_OBFUSCATE() so App ID is not directly embedded in executable
	const std::string secretAppID{ SIV3D_OBFUSCATE(PHOTON_APP_ID) };

	// Class for communicating with server
	// - Photon App ID
	// - Version of this application (cannot communicate with programs with different versions)
	// - Whether to enable debug output via Print
	MyNetwork network{ secretAppID, U"1.0", Verbose::Yes };

	while (System::Update())
	{

	}
}

75.3 Connecting to Server

Connecting to Server

  • Connect to the server with MyNetwork's .connect()
  • Set your own name (username) as an argument
  • After this, a string combining the username with random numbers is automatically assigned as the user ID

Synchronizing with Server

  • After calling .connect(), .isActive() returns true
  • During this time, you need to call .update() at 60 FPS frequency to continue synchronizing with the server
  • If .update() is not called for several seconds, you may be disconnected from the server
  • Calling .update() when not connected to the server does nothing
  • The "functions called when ~" mentioned in later sections are basically called at the timing of .update()

Disconnecting from Server

  • The MyNetwork destructor automatically handles disconnection from the server, so explicit .disconnect() is not necessary
Code 
# include <Siv3D.hpp>
# include "Multiplayer_Photon.hpp"
# include "PHOTON_APP_ID.SECRET"

class MyNetwork : public Multiplayer_Photon
{
public:

	using Multiplayer_Photon::Multiplayer_Photon;
};

void Main()
{
	Window::Resize(1280, 720);
	const std::string secretAppID{ SIV3D_OBFUSCATE(PHOTON_APP_ID) };
	MyNetwork network{ secretAppID, U"1.0", Verbose::Yes };

	while (System::Update())
	{
		// Synchronize with server if connected
		network.update();

		// Button to connect to server
		if (SimpleGUI::Button(U"Connect", Vec2{ 1000, 20 }, 160, (not network.isActive())))
		{
			// Username
			const String userName = U"Siv";

			// Connect to server
			network.connect(userName);
		}
	}

	// Disconnect from server
	// Automatically disconnected by Multiplayer_Photon destructor, so no need to call explicitly
	// network.disconnect();
}

75.4 Customizing Function to Handle Server Connection Results

Overriding connectReturn()

  • Multiplayer_Photon::connectReturn() is a function that handles the result of attempting to connect to the server
  • You can customize the processing by overriding this.
Code 
# include <Siv3D.hpp>
# include "Multiplayer_Photon.hpp"
# include "PHOTON_APP_ID.SECRET"

class MyNetwork : public Multiplayer_Photon
{
public:

	using Multiplayer_Photon::Multiplayer_Photon;

private:

	// Override and customize the function that handles server connection attempt results
	void connectReturn([[maybe_unused]] const int32 errorCode, const String& errorString, const String& region, [[maybe_unused]] const String& cluster) override
	{
		if (m_verbose)
		{
			Print << U"MyNetwork::connectReturn() [Handle server connection attempt result]";
		}

		if (errorCode) // If server connection failed, errorCode is non-zero
		{
			if (m_verbose)
			{
				Print << U"[Server connection failed] " << errorString;
			}

			return;
		}

		if (m_verbose)
		{
			Print << U"[Server connection successful]";
			Print << U"[region: {}]"_fmt(region);
			Print << U"[Username: {}]"_fmt(getUserName());
			Print << U"[User ID: {}]"_fmt(getUserID());
		}

		// Set background color to blue
		Scene::SetBackground(ColorF{ 0.4, 0.5, 0.6 });
	}
};

void Main()
{
	Window::Resize(1280, 720);
	const std::string secretAppID{ SIV3D_OBFUSCATE(PHOTON_APP_ID) };
	MyNetwork network{ secretAppID, U"1.0", Verbose::Yes };

	while (System::Update())
	{
		network.update();

		if (SimpleGUI::Button(U"Connect", Vec2{ 1000, 20 }, 160, (not network.isActive())))
		{
			const String userName = U"Siv";
			network.connect(userName);
		}
	}
}

[Note: This is a shortened version of the multiplayer tutorial covering the basic setup and connection. The full tutorial contains additional sections on rooms, messaging, and complete multiplayer game examples.]