vercel/errors/now-static-build-failed-to-detect-a-server.md

@now/static-build Failed to detect a server running

Why This Warning Occurred

When running now dev, the @now/static-build builder proxies relevant HTTP requests to the server that is created by the now-dev script in the package.json file.

In order for now dev to know which port the server is running on, the builder is provided a $PORT environment variable that the server must bind to. The error "Failed to detect a server running on port" is printed if the builder fails to detect a server listening on that specific port within five minutes.

Possible Ways to Fix It

Please ensure that your now-dev script binds the spawned development server on the provided $PORT that the builder expects the server to bind to.

For example, if you are using Gatsby, your now-dev script must use the -p (port) option to bind to the $PORT specified from the builder:

In Windows environments, reference the PORT environment variable with %PORT%

{
  ...
  "scripts": {
    ...
    "now-dev": "gatsby develop -p $PORT"
  }
}

Consult your static builder program's --help or documentation to figure out what the command line flag to bind to a specific port is (in many cases, it is one of: -p / -P / --port).