After second emit, socket.io throw net::ERR_CONNECTION_REFUSED error

Question

I send a message from backend to the front-end with socket.io and I can see it. But after I try manually to add a second one I got a connection refused error. Why is this? How can I solve it?

Backend code:

const options = {
  cors: true,
  origins: ["http://127.0.0.1:" + port],
};
const io = new Server(server, options);

/**
 *  socket connections
 */

io.use((socket, next) => {
  if (socket?.handshake?.auth?.token) {
    new Promise((resolve, reject) => {
      jwt.verify(socket.handshake.auth.token, "Bearer", (error, result) => {
        if (error) reject(next(new Error(error)));

        resolve(next());
      });
    });
  } else {
    next(new Error("invalid"));
  }
}).on("connection", async function (socket) {
  socket.on("hi", (a) => console.log(a.toUpperCase()));
  console.log("is this working?? ");
  // console.log("DB ", Log);
  socket.emit("message", "socket connection is up"); ;
  try {
    Log.log.addHook("afterSave", "notifyUsers", (log, options) => {
      console.log("NEW LOG ???", log);
      socket.emit("logs", log);
    });
  } catch (error) {
    console.log("ERRR ", error);
  }
});

Front-end:

  const socket = io(API_URL, {
      reconnectionDelayMax: 10000,
      auth: {
        token: localStorage.getItem("access_token"),
      },
    });
    props.setSocket(socket);
    socket.emit("hi", "Hello from client!");
    socket.on("message", function (data) {
      console.log("message ", data);
    });