diff --git a/server/src/index.ts b/server/src/index.ts
index 06444a1..e1faf6e 100644
--- a/server/src/index.ts
+++ b/server/src/index.ts
@@ -1,3 +1,4 @@
+import { createServer } from 'node:http';
 import Fastify from 'fastify';
 import cors from '@fastify/cors';
 import { PORT } from './config.js';
@@ -5,13 +6,22 @@ import { runMigrations } from './db/migrate.js';
 import { healthRoutes } from './routes/health.js';
 import { shipRoutes } from './routes/ships.js';
 import { weaponRoutes } from './routes/weapons.js';
+import { setupSocketIO } from './socket/index.js';
 
-const app = Fastify({ logger: true });
+// Create a raw HTTP server so both Fastify and Socket.IO can share it
+const httpServer = createServer();
+const app = Fastify({ logger: true, serverFactory: (handler) => {
+  httpServer.on('request', handler);
+  return httpServer;
+}});
 
 const start = async () => {
   try {
     runMigrations();
 
+    // Set up Socket.IO on the shared HTTP server
+    setupSocketIO(httpServer);
+
     await app.register(cors, { origin: true });
     await app.register(healthRoutes);
     await app.register(shipRoutes);
diff --git a/server/src/socket/index.ts b/server/src/socket/index.ts
new file mode 100644
index 0000000..9860d69
--- /dev/null
+++ b/server/src/socket/index.ts
@@ -0,0 +1,25 @@
+import { Server } from 'socket.io';
+import type { Server as HttpServer } from 'node:http';
+import { registerShipEvents } from './ship-events.js';
+import { registerWeaponEvents } from './weapon-events.js';
+
+export function setupSocketIO(httpServer: HttpServer): Server {
+  const io = new Server(httpServer, {
+    cors: {
+      origin: true,
+    },
+  });
+
+  io.on('connection', (socket) => {
+    console.log(`Client connected: ${socket.id}`);
+
+    registerShipEvents(io, socket);
+    registerWeaponEvents(io, socket);
+
+    socket.on('disconnect', () => {
+      console.log(`Client disconnected: ${socket.id}`);
+    });
+  });
+
+  return io;
+}
diff --git a/server/src/socket/ship-events.ts b/server/src/socket/ship-events.ts
new file mode 100644
index 0000000..1efc129
--- /dev/null
+++ b/server/src/socket/ship-events.ts
@@ -0,0 +1,49 @@
+import type { Server, Socket } from 'socket.io';
+import { updateShipSchema } from '../validation/ship-schema.js';
+import * as shipService from '../services/ship-service.js';
+
+export function registerShipEvents(io: Server, socket: Socket) {
+  socket.on('ship:join', ({ shipId }: { shipId: string }) => {
+    socket.join(shipId);
+
+    // Send current state to the joining client
+    const result = shipService.getShip(shipId);
+    if (result) {
+      socket.emit('ship:state', result);
+    } else {
+      socket.emit('ship:error', { message: 'Ship not found' });
+    }
+  });
+
+  socket.on('ship:leave', ({ shipId }: { shipId: string }) => {
+    socket.leave(shipId);
+  });
+
+  socket.on('ship:update', ({ shipId, patch }: { shipId: string; patch: unknown }) => {
+    const parsed = updateShipSchema.safeParse(patch);
+    if (!parsed.success) {
+      socket.emit('ship:error', {
+        message: 'Validation failed',
+        details: parsed.error.issues,
+      });
+      return;
+    }
+
+    try {
+      const ship = shipService.updateShip(shipId, parsed.data);
+      if (!ship) {
+        socket.emit('ship:error', { message: 'Ship not found' });
+        return;
+      }
+
+      // Broadcast to all clients in the room (including sender)
+      io.to(shipId).emit('ship:patched', {
+        shipId,
+        patch: parsed.data,
+        updated_at: ship.updated_at,
+      });
+    } catch (err: any) {
+      socket.emit('ship:error', { message: err.message });
+    }
+  });
+}
diff --git a/server/src/socket/weapon-events.ts b/server/src/socket/weapon-events.ts
new file mode 100644
index 0000000..12b5159
--- /dev/null
+++ b/server/src/socket/weapon-events.ts
@@ -0,0 +1,70 @@
+import type { Server, Socket } from 'socket.io';
+import { createWeaponSchema, updateWeaponSchema } from '../validation/weapon-schema.js';
+import * as weaponService from '../services/weapon-service.js';
+
+export function registerWeaponEvents(io: Server, socket: Socket) {
+  socket.on(
+    'weapon:create',
+    ({ shipId, weapon }: { shipId: string; weapon: unknown }) => {
+      const parsed = createWeaponSchema.safeParse(weapon);
+      if (!parsed.success) {
+        socket.emit('ship:error', {
+          message: 'Validation failed',
+          details: parsed.error.issues,
+        });
+        return;
+      }
+
+      try {
+        const created = weaponService.createWeapon(shipId, parsed.data);
+        io.to(shipId).emit('weapon:created', { shipId, weapon: created });
+      } catch (err: any) {
+        socket.emit('ship:error', { message: err.message });
+      }
+    },
+  );
+
+  socket.on(
+    'weapon:update',
+    ({ weaponId, patch }: { weaponId: string; patch: unknown }) => {
+      const parsed = updateWeaponSchema.safeParse(patch);
+      if (!parsed.success) {
+        socket.emit('ship:error', {
+          message: 'Validation failed',
+          details: parsed.error.issues,
+        });
+        return;
+      }
+
+      try {
+        const weapon = weaponService.updateWeapon(weaponId, parsed.data);
+        if (!weapon) {
+          socket.emit('ship:error', { message: 'Weapon not found' });
+          return;
+        }
+
+        io.to(weapon.ship_id).emit('weapon:patched', {
+          shipId: weapon.ship_id,
+          weaponId,
+          patch: parsed.data,
+          updated_at: weapon.updated_at,
+        });
+      } catch (err: any) {
+        socket.emit('ship:error', { message: err.message });
+      }
+    },
+  );
+
+  socket.on('weapon:delete', ({ weaponId }: { weaponId: string }) => {
+    const result = weaponService.deleteWeapon(weaponId);
+    if (!result) {
+      socket.emit('ship:error', { message: 'Weapon not found' });
+      return;
+    }
+
+    io.to(result.shipId).emit('weapon:deleted', {
+      shipId: result.shipId,
+      weaponId,
+    });
+  });
+}