setupClientWaitingUI <div>
Add ever dependency
Refactor; add 'host server' button in client-only mode
Remove ever dependency; use DOM events directly

ever(button).once('click', ...) was crashing in:

EventEmitter.prototype.once = function(type, listener) {
  if (!isFunction(listener))
    throw TypeError('listener must be a function');

  var fired = false;

  function g() {
    this.removeListener(type, g); // <-- TypeError, 'this' was button (DOM node, has removeEventListener not wrapped removeListener - this/scope error?)
Fix missing selves
Remove button on click - starting a the server instance works
Remove client waiting UI when client-only instance connects to remote server, too