Chess

A client-server application written in Java that uses Socket programming which enables communication between two devices. It uses files for persistency.

Main Idea and Requirements

Create a console-based chess game. The game should be designed as client-server application. One server should be able to host many players and games. For the sake of simplicity you can use Sockets and your own communication protocol. Use files for persistency.

Server functionalities:

• Manage users. User can register and then login. The server should keep username/password, name and some statistics for each user (played games, won games). Optionally you can think about a rating system based on game results.
• Manage games. Users can request a game and when two users are available for a game the server creates one and assigns them. Optionally the user matching can be based on rating similarity.
• Record games. For each game, track the time and moves. The server should validate each move and if not legal should return to the client meaningful message with reason, like “Can’t move bishop to g5: illegal move”. Also the server should detect situations like “Check” or “Checkmate” and display them to the user.
• In case a player runs out of time - end the game and notify the clients to display win/lose screens.

Client functionalities:

• Register/login to the server
• View own statistics
• Review played games (list of games, date, opponent, win/loss) as well as review the moves in the game.
• Start new game

Additions:

• Gameplay – draw the board, accept input as any notation (for example portable game notation or your own one), send the move to the server and redraw the board.
• There should be an option to offer draw (could be accepted or declined by the other user) or surrender.
• Show statistics for the game.
• In case of closing the client or network error, the user should be able to restart the client within one minute before getting dropped from the game. In case the client (console app) is restarted and there is an ongoing game – the user should directly enter the game.

TLS (optional)

TLS is disabled by default for local development. To enable TLS, create a keystore and pass the system properties for both server and client.

Create a local self-signed keystore (PKCS12):

keytool -genkeypair -alias chess-server -keyalg RSA -keysize 2048 -validity 365 -storetype PKCS12 -keystore C:\path\to\chess-server.p12 -storepass changeit -dname "CN=localhost, OU=Dev, O=Chess, L=Local, ST=NA, C=US" -ext "SAN=DNS:localhost,IP:127.0.0.1"

Server properties:

-Dchess.tls.enabled=true
-Dchess.tls.keystore=C:\path\to\chess-server.p12
-Dchess.tls.keystore.password=changeit
-Dchess.tls.keystore.type=PKCS12

Client properties:

-Dchess.tls.enabled=true
-Dchess.tls.truststore=C:\path\to\chess-server.p12
-Dchess.tls.truststore.password=changeit
-Dchess.tls.truststore.type=PKCS12

Hostname verification is enabled by default, so the certificate must include the host you connect to (the SAN above covers localhost and 127.0.0.1).

Metrics (knobs)

The server logs periodic metrics and can emit warnings when thresholds are exceeded. Configure via system properties:

• chess.metrics.log.enabled (default: true)
• chess.metrics.log.intervalMs (default: 60000)
• chess.metrics.alert.enabled (default: true)
• chess.metrics.alert.connections.current (disabled if <= 0)
• chess.metrics.alert.matchmaking.queue (disabled if <= 0)
• chess.metrics.alert.active.games (disabled if <= 0)
• chess.metrics.alert.heap.used.pct (disabled if <= 0)
• chess.metrics.alert.error.rate.pct (default: 5.0)
• chess.metrics.export.enabled (default: false)
• chess.metrics.export.path (default: logs/metrics.json)
• chess.metrics.export.format (default: json, also supports ndjson)

Prometheus exporter (HTTP scrape endpoint):

• chess.metrics.prometheus.enabled (default: false)
• chess.metrics.prometheus.host (default: 0.0.0.0)
• chess.metrics.prometheus.port (default: 9102)
• chess.metrics.prometheus.path (default: /metrics)