Member Avatar for bondito

Hi there, i was thinking of building an instant messaging systemon a LAN, for my final year project. Dont know how to go about it, really need ideas. I was planning on using java sockets to create the system. Any helpful tips will be really appreciated.

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  • Latest Post Latest Post by jwenting

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A clear split exists between two sensible project directions mentioned in this thread: reuse an existing protocol (as suggested — XMPP/Jabber) to get presence, routing and multi-network support for free; or build a custom TCP-based server with Java sockets to learn protocol design, threading and reliability. ’s nudge to research is valid, but a short, concrete plan helps turn that research into deliverables.

Essential features to aim for (minimal viable demo): presence (online/away), one-to-one messaging, offline message queue, simple authentication, and a basic GUI that never blocks the UI thread. Optional stretch goals: group chat (rooms), file transfer (separate socket or HTTP upload), message persistence (lightweight DB), and TLS for transport. Architecture choice: client–server is simplest on a LAN; P2P adds NAT/firewall complexity and is not necessary for a campus LAN demo.

A compact server pattern that works for a semester project — thread pool + newline-delimited JSON messages and a concurrent user map. Example sketch:

ServerSocket server = new ServerSocket(5555);
ExecutorService pool = Executors.newFixedThreadPool(50);
ConcurrentMap<String, ClientSession> sessions = new ConcurrentHashMap<>();

while (true) {
  Socket sock = server.accept();
  pool.submit(() -> handleClient(sock, sessions));
}

/* handler: read lines (UTF-8), parse JSON {type,from,to,body},
   route to sessions.get(to).send(...) or queue if offline */

Message example (newline-terminated):

{"type":"message","from":"alice","to":"bob","body":"Hello"}

Testing and pitfalls: simulate many clients to check thread usage and latency; prefer a fixed thread pool or switch to NIO for high scale; use heartbeats/timeouts to detect dead peers; guard shared maps with concurrent collections; close sockets in finally blocks to avoid leaks. If deadline is tight, adopt an XMPP library/server and focus the project on UI/UX, an XMPP extension, protocol analysis, or performance comparisons.

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Member Avatar for BigBlueBall

I suggest starting by looking at an open protocol -- namely Jabber. There are plenty of code examples and you'll have the added advantage of being able to add multi-network support (if desired). You might also be able to enlist some help from BigBlueBall as well.

Member Avatar for jwenting

There's thousands of people doing that, millions of resources on the net about it.
Just use a search engine instead of sitting here waiting for someone to do it all for you.

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