SocketSpeak

SocketSpeak is a CLI messaging app written in C for local-area-network peer chat. It supports peer-to-peer one-on-one conversations, group chat, ASCII-art stickers, and a synchronous Hangman minigame. The project is designed to stay lightweight and dependency-free beyond a C compiler, make, and pthreads.

Features

• Peer-to-peer auto-discovery over UDP broadcast for one-on-one chat.
• Group chat through a central group server.
• Persistent storage for usernames, chat history, and stickers under ~/lmp/<username>/.
• ASCII-art sticker creation, preview, and sending.
• Group-only Hangman gameplay.
• Tested on Linux (Debian) and macOS.

Prerequisites

• GCC or Clang
• make
• A POSIX-like environment with pthread support

The project is compiled in ANSI C mode with pedantic checks enabled through the Makefile.

Build

make

This builds the main binaries in bin/:

• bin/main - One-on-One Chat
• bin/gserver - Group Chat
• bin/gclient - Group Chat

It also builds the test binaries under bin/.

Usage

One-on-One Chat (P2P)

Start either peer with the main binary:

./bin/main [-u <username>]

The -u flag sets the program username used for persistent storage. If omitted, the program uses default as program username.

Runtime flow:

1. Each peer broadcasts its local IPv4 address over UDP to 255.255.255.255:8082.
2. The program waits up to 5 seconds for an incoming TCP connection on port 8081.
3. If a connection arrives, that instance acts as the client side inside the application.
4. If the accept times out, the instance switches to UDP discovery mode and waits for another peer to broadcast.
5. When a broadcast is received, it connects back over TCP to port 8081 and acts as the server side inside the application.

Group Chat (Group)

Start the group server:

./bin/gserver

Connect a group client:

./bin/gclient

The group client broadcasts a UDP discovery signal, waits for a server response, and then connects over TCP.

Commands

Once connected, plain text is sent as a message. Commands are prefixed with /.

Command	Description	Mode
plain text	Send a plain-text message	P2P, Group
/msg <text>	Explicitly send a message	P2P, Group
/nick <name>	Set your nickname and persist it	P2P, Group
/sticker <action> ...	Create, send, list, or preview ASCII-art stickers	P2P
/gi	Display group info, including member nicknames and UIDs	Group
/load	Request and display group message history	Group
/hangman <action>	Start, join, or exit the Hangman game	Group
/meow <text>	Demo command	P2P, Group

Stickers

Stickers can be created, listed, previewed, and sent with the /sticker command in P2P chat only.

/sticker create <sticker_name>
/sticker send <sticker_name>
/sticker list
/sticker preview <sticker_name>

• create opens a multiline terminal editor for drawing the sticker.
• Press ESC to finish editing and save the sticker.
• Stickers are stored in ~/lmp/<username>/saved_stickers.txt.
• send the sticker to other peers in the chat.
• preview shows the sticker locally without sending it.

Hangman

Hangman is available in group chat only.

/hangman start
/hangman join
/hangman exit

• start initializes a new game.
• join joins an active game.
• exit leaves the game and returns to normal messaging.

LAN Messaging Protocol

SocketSpeak uses a custom binary framing protocol called LMP. Each frame is an 8-byte header followed by a variable-length payload.

Field	Size	Description
Magic	2 bytes	Fixed value 0x4C4D (LM)
Type	1 byte	Command or message type
Reserved	1 byte	Reserved for future use
Payload length	4 bytes	Big-endian uint32 payload size
Payload	N bytes	Message body

The payload length supports messages up to 4 GB.

Storage

User data (P2P and Group Client)

Client-side user data is stored under ~/lmp/<username>/, including:

• uid.txt for the local user UID
• nick.txt for the current nickname
• saved_stickers.txt for sticker definitions (P2P sticker feature)
• peers/<peer_uid>/nick.txt for a peer's saved nickname (P2P)
• peers/<peer_uid>/history.txt for one-on-one chat history with that peer (P2P)

This makes user-specific state persistent across sessions.

Server data (Group)

Group chat history is stored on the group server under ~/lmp/server/<group_uid>/:

• history.txt for chat history