WORTH — Real‑Time Kanban in Java

Collaboration, built from the sockets up.

WORTH (WORkTogetHer) is a complete client-server system for teams: users register and log in, create projects, add members, put cards on a Kanban board and move them through their life cycle, see who is online and talk in a chat that belongs to each project.

The constraint was the interesting part: no frameworks. Every networking primitive comes from the Java standard library, and each kind of interaction gets the mechanism that suits it, from reliable request-response to server push and group messaging.

One mechanism per job.

Many clients, one consistent state.

The main thread restores the saved state, starts the RMI registry and blocks on accept(). Every connection goes to a cached thread pool, where a worker reads the client's requests, runs them against the shared core and sends back the response. Shared users and projects are guarded by synchronized blocks, so concurrent updates stay atomic and consistent.

• Fault tolerance. An abrupt disconnection is detected through the stream's end of file: the user is logged out, the socket closed and the stale callback stub pruned.
• Client threads. The client runs its command line and TCP traffic on the main thread, receives callbacks on an RMI thread, and starts one listener thread per project chat that stores messages until the user reads them.
• Address pool. Each new project takes the smallest free multicast address from a sorted TreeSet, and gives it back when the project is deleted: 8,192 chats in total.

A board the server enforces.

Every card starts in todo and moves according to fixed rules. Any other move is rejected with MOVE_CARD_FORBIDDEN; every valid one is recorded in the card's history and announced in the project chat, as in the demo at the top.

// source and destination must be different listsif (sourceList.equals(destList)) {    message.setResponse(Response.CARD_EXISTS);    return message;}// the Kanban rules, checked on every moveswitch (destList) {    case "todo" :        message.setResponse(Response.MOVE_CARD_FORBIDDEN);        return message;    case "inprogress" :        if (sourceList.equals("done")) {            message.setResponse(Response.MOVE_CARD_FORBIDDEN);            return message;        }        break;    case "toberevised" :        if (!sourceList.equals("inprogress")) {            message.setResponse(Response.MOVE_CARD_FORBIDDEN);            return message;        }        break;    case "done" :        if (sourceList.equals("todo")){            message.setResponse(Response.MOVE_CARD_FORBIDDEN);            return message;        }        break;    default :}synchronized (createdProjects) {    // the card must really be in the source list    int cardIndex = sList.indexOf(new Card(cardName, null));    if (cardIndex == -1) {        message.setResponse(Response.NONEXISTENT_CARD);        return message;    }    // move the card, update its history, persist the project    Card card = sList.remove(cardIndex);    card.updateHistory(destList);    dList.add(card);    int cardIndex2 = project.getCards().indexOf(card);    project.getCards().set(cardIndex2, card);    server.saveProject(project);}

Passwords are never stored.

Credentials are hashed with PBKDF2-HMAC-SHA1, a 32-byte random salt and 20,000 iterations, and only the salted hash reaches the disk. It is the small detail that separates a student exercise from a system you could actually trust with a team's accounts.