Web drive manager shutting down

i am trying to run protractor with code ample that i found online right after i am writing protractor config.js the web drive manager shutting down. i have google chrome installed but firefox is my default browser and i wondered if its related to the problem

here is the code: todo-spec.js

    describe('angularjs homepage todo list', function() {
it('should add a todo', function() {
browser.get('https://angularjs.org');

element(by.model('todoList.todoText')).sendKeys('write first protractor test');
element(by.css('[value="add"]')).click();

var todoList = element.all(by.repeater('todo in todoList.todos'));
expect(todoList.count()).toEqual(3);
expect(todoList.get(2).getText()).toEqual('write first protractor test');

// You wrote your first test, cross it off the list
todoList.get(2).element(by.css('input')).click();
var completedAmount = element.all(by.css('.done-true'));
expect(completedAmount.count()).toEqual(2);
});
});

config.js

    exports.config = {
seleniumAddress: 'http://localhost:4444/wd/hub',
specs: ['todo-spec.js']
};