Not able to run basic test using webdriver IO - webdriver-io

Question

I am new to webdriver I am trying to run following code
var assert = require('assert');
describe('webdriver.io page', function() {
it('should have the right title', function () {
browser.url('/');
var title = browser.getTitle();
assert.equal(title,'WebDriverIO - Selenium 2.0 javascript bindings for nodejs');
});
});
When I am trying to run $npm test it is giving me following exception
> web-wedio#1.0.0 test /Users/user_namej/Downloads/web-wedio
> wdio
A service failed in the 'onPrepare' hook
Error: Selenium exited before it could start
Another Selenium process may already be running or your java version may be out of date.
Be sure to check the official Selenium release notes for minimum required java version: https://raw.githubusercontent.com/SeleniumHQ/selenium/master/java/CHANGELOG
at ChildProcess.errorIfNeverStarted (/Users/user_namej/Downloads/web-wedio/node_modules/selenium-standalone/lib/start.js:158:10)
at ChildProcess.emit (events.js:159:13)
at Process.ChildProcess._handle.onexit (internal/child_process.js:209:12)
Continue...
[23:57:43] COMMAND POST "/wd/hub/session"
ERROR: Error forwarding the new session Empty pool of VM for setup Capabilities [{rotatable=true, locationContextEnabled=true, loggingPrefs=org.openqa.selenium.logging.LoggingPreferences#9288a03, browserName=firefox, javascriptEnabled=true, handlesAlerts=true, maxInstances=5, requestOrigins={name=webdriverio, version=4.13.1, url=http://webdriver.io}}]
firefox
at new RuntimeError (/Users/user_namej/Downloads/web-wedio/node_modules/webdriverio/build/lib/utils/ErrorHandler.js:143:12)
at Request._callback (/Users/user_namej/Downloads/web-wedio/node_modules/webdriverio/build/lib/utils/RequestHandler.js:316:39)
at Request.self.callback (/Users/user_namej/Downloads/web-wedio/node_modules/request/request.js:185:22)
at Request.emit (events.js:159:13)
at Request.<anonymous> (/Users/user_namej/Downloads/web-wedio/node_modules/request/request.js:1157:10)
at Request.emit (events.js:159:13)
at IncomingMessage.<anonymous> (/Users/user_namej/Downloads/web-wedio/node_modules/request/request.js:1079:12)
at Object.onceWrapper (events.js:254:19)
at IncomingMessage.emit (events.js:164:20)
at endReadableNT (_stream_readable.js:1062:12)
I try . to shut down server using
http://localhost:4444/selenium-server/driver/?cmd=shutDownSeleniumServer
but it is redirecting to 500 error page,Also I tried to do it with different commands
lsof -i :4444
kill -9 $(lsof -ti tcp:4444)
Still not working.What should I do.
Please let me know if more details required

Answer 1

Silly question, but have you checked your java version to see if it's compatible?
If not, maybe this could help explain your problem: https://github.com/SeleniumHQ/selenium/issues/2043