const getRoomId = (user1, user2) => {
return [user1, user2].sort().join('_'); // e.g., "123_456"
};
// When a user sends a message
socket.on('send_message', (data) => {
const { sender, receiver, message } = data;
const roomId = getRoomId(sender, receiver);
io.to(roomId).emit('receive_message', message);
// Save to database here
});