DocSpace-buildtools/common/ASC.Socket.IO/app/portalManager.js

const portalInternalUrl = require("../config").get("portal.internal.url");
module.exports = (req) => {
  if (portalInternalUrl) return portalInternalUrl;

  const xRewriterUrlInternalHeader = "x-rewriter-url-internal";
  if (req.headers && req.headers[xRewriterUrlInternalHeader]) {
    return req.headers[xRewriterUrlInternalHeader];
  }

  const xRewriterUrlHeader = "x-rewriter-url";
  if (req.headers && req.headers[xRewriterUrlHeader]) {
    return req.headers[xRewriterUrlHeader];
  }

  if (req?.headers?.origin) {
    return req.headers.origin;
  }

  return "";
};