Here are the classes, structs, unions and interfaces with brief descriptions:

CClientData	ClientData is a struct which contains the username of a client and its port number. It is used by the Lobby class to provide an easy way to differentiate the clients in a game and facilitate the packet communications between them
CClientNetworkInterface	ClientNetworkInterface is an interface to communicates with a server
CClientNetworkManager	ClientNetworkManager is the implementation of the ClientNetworkInterface. It manages the communications with the server and owns the client's socket
CClientPacket	ClientPacket is an object containing data that a client wishes to send to the server and its remote port. This struct must be used in the server side only
CHttpInterface	HttpInterface is an interface to perform GET and POST requests via the HTTP protocol. All requests must have a json body
CHttpManager	HttpManager is an implementation of the HttpInterface which enable to send Http GET and POST requests with a json body using a sf::Http object
CLobby	Lobby is a class which provides a simple, naive way of differentiating between the different clients connected to the server. It uses the ClientData struct to simplify packet communications between two players in a game
CPlayerData	PlayerData is a struct containing the username of a player and its elo
CServerNetworkInterface	ServerNetworkInterface is an interface to communicates with multiple clients
CServerNetworkManager	ServerNetworkManager is an implementation of the NetworkInterface which manages network communications between the server and the clients