The next.js assetPrefix needs to be included in the websocket URL. Previously, we were appending both assetPrefix and basePath, which is incorrect. `assetPrefix` overrides `basePath` if both are set. This PR mimics the way Next.js connects to the HMR server. Sources: - https://github.com/AlessioGr/next.js/blob/canary/packages/next/src/server/lib/router-server.ts#L688 - https://github.com/AlessioGr/next.js/blob/canary/packages/next/src/server/config.ts#L322 - https://github.com/AlessioGr/next.js/blob/canary/packages/next/src/client/components/react-dev-overlay/app/client-entry.tsx