Using socket.io with React and Google App Engine - node.js

Question

I've created a Node(express)/React app that uses socket.io and Redux's store as follows:
import io from "socket.io-client";
import * as types from "../actions/types";
import { cancelReview, startReview } from "./actions";
const socket = io("http://localhost:8080", {
transports: ["websocket"]
});
export const init = store => {
socket.on("connect", () => {
console.log("websocket connection successful...");
socket.on("cancelReview", (id, name) => {
cancelReview(store, id, name);
});
socket.on("startReview", (id, name) => {
startReview(store, id, name);
});
});
};
This function is then called from store.js as follows:
import { createStore, applyMiddleware } from "redux";
import { composeWithDevTools } from "redux-devtools-extension/developmentOnly";
import thunk from "redux-thunk";
import rootReducer from "./reducers";
import { init } from "./socket/socket";
// Initial state
const initialState = {};
// Middleware
const middleware = [thunk];
const store = createStore(
rootReducer,
initialState,
composeWithDevTools(applyMiddleware(...middleware))
);
init(store);
export default store;
Everything works fine on my local machine, but I'm now realizing after doing some research that this will not work on Google's app engine because instead of http://localhost:8080 I need to get the actual IP address from Google's metadata server and pass in EXTERNAL_IP + ":65080". So I'm able to get the external IP in my express app as follows:
const METADATA_NETWORK_INTERFACE_URL =
"http://metadata/computeMetadata/v1/instance/network-interfaces/0/access-configs/0/external-ip";
function getExternalIp(cb) {
const request = axios.create({
baseURL: METADATA_NETWORK_INTERFACE_URL,
headers: { "Metadata-Flavor": "Google" }
});
request
.get("/", (req, res) => {
return cb(res.data);
})
.catch(err => {
console.log("Error while talking to metadata server, assuming localhost");
return cb("localhost");
});
}
However, if I pass this value into my render function as seen below, React creates a prop to pass into components (as far as I understand from the info I could find):
app.get("*", (req, res) => {
getExternalIp(extIp => {
res.render(path.resolve(__dirname, "client", "build", "index.html"), {
externalIp: extIp
});
});
I am not able to access this value via the window global. So my question is, how do I access this external IP from my store initialization, since it is not an actual React component?
Thanks in advance.