android studio error Error:Connection timed out

Question

I just create a new Project in the android studio and add gcm module to it.
and I keep giving this error message

Error:Connection timed out: connect. If you are behind an HTTP proxy, please configure the proxy settings either in IDE or Gradle.      

and I do not use any proxy.
can anyone help me about this?

Update
now after rebuild my project i give this error

Error:A problem occurred configuring project ':app'.    
 A problem occurred configuring project ':backend'.
Could not resolve all dependencies for configuration ':backend:classpath'.
   Could not resolve com.google.appengine:gradle-appengine-plugin:1.9.18.
    Required by:
        PushStart:backend:unspecified
      Could not resolve com.google.appengine:gradle-appengine-plugin:1.9.18.
      Could not get resource 'https://jcenter.bintray.com/com/google/appengine/gradle-appengine-plugin/1.9.18/gradle-appengine-plugin-1.9.18.pom'.
      Could not GET 'https://jcenter.bintray.com/com/google/appengine/gradle-appengine-plugin/1.9.18/gradle-appengine-plugin-1.9.18.pom'.
      Connection to https://jcenter.bintray.com refused

Answer 1

Just try Invalidate Caches.. Goto File->Invalidate Caches/Restart->Choose "Invalidate and Restart".