OK I see that you tried to reuse the suggestions from the previous diffs reviews. However there is a simpler and better solution: create a startup function.

Now that the message parsing has been emptied, the logic for block connection can be moved into its own function (say handleBlockConnected(hash, height).

Then your startup function can look like so:

function startup() {
    console.log('App startup, catching up to the current tip');

    {tipHash, tipHeight} = someWayToGatherTheHashAndHeight();

    handleBlockConnected(tipHash, tipHeight);
}

However there is a simpler and better solution: create a startup function.

Good point.

I've created stub methods for these functions. Unit tests for the app startup function will be added when the function does something.