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General Structure

The server code consists of the following top level modules (in order of inclusion):

core : contains the types necessary to implement the server logic.
protocol : contains definitions of network protocol messages and code for their (de)serialization.
handlers : acts on parsed protocol messages to modify the server state and generate responses to network clients.
server : contains the code for IO handling.
main : starts the server and runs the main event poll.

core::client::HwClient and core::room::HwRoom structures are where the most of the game-related data is stored. They are often referenced by core::types::{ClientId, RoomId} identifiers
core::server::HwServer is a collection HwClient s and HwRoom s with some additional global server data, and is responsible for maintaining related invariants. For this reason it doesn't provide a public way to retrieve a mutable HwClient or HwRoom reference.
core::anteroom::HwAnteroom stores clients that did not yet complete the logic procedure. Those clients are represented by core::anteroom::HwAnteroomClient structure, that only contains a relevant subset of full client data.
core::server::HwRoomControl can be requested from a HwServer to modify a room that the current client is located in. This interface is not directly provided by HwServer to avoid constant checks to ensure the client is still in the room.

protocol::messages::HwProtocolMessage is a parsed representation of a message from a client.
protocol::messages::HwServerMessage is a messaged generated by the server to be deserialized into text protocol and sent to a client.
protocol::ProtocolDecoder is an entry point to the network protocol parser.

handlers::Response is the structure handlers use for queueing server messages to be sent out, clients to be removed due to server logic, and IO tasks to be performed asynchronously.
handlers::IoTask type represents a task for the IO thread than can be queued using Response . The task result will eventually be returned as a handlers::IoResult value.

server::io::IoThread represents the thread for handling all IO processing apart from writing/reading from clients' network sockets.
server::network::NetworkClient is a structure complements a HwClient with data relevant to network connection handling. A NetworkClient is referenced by the same ClientId as the corresponding HwClient .
server::network::NetworkLayer is the top level structure that contains an IoThread , a HwAnteroom , a HwServer , and a collection of NetworkClients . It handles all the dispatching between all these components.

A new client is first created by the NetworkLayer when a network connection is established. The relevant network state is stored in a NetworkClient structure.
If the server is built with TLS support, the client will remain in server::network module until the TLS handshake is completed.
Either way, after the connection is successfully established, a new HwAnteroomClient structure is created for the client and stored in the HwAnteroom
From there on, when new data received on client's socked, it's parsed by a ProtocolDecoder and the resulting HwProtocolMessage is passed into handlers module for further dispatching
While some general messages are processed directly by handlers , the ones only available in a specific context are passed into a specialized submodule: handlers::inanteroom for clients located in HwAnteroom , handlers::inroom for HwServer clients that are in a HwRoom and handlers::inlobby for those that aren't.
When processing of a HwProtocolMessage results in a HwAnteroomClient being successfully logged in, it's immediately moved into the HwServer and extended to a full HwClient .
If a handler needs complete remove a client, apart from removing it from HwAnteroom of HwServer it will also queue a request to delete the corresponding NetworkClient on it's Response .