I remove ws folder from node_modules. After that, I execute npm install --save ws and version 3.3.3 was installed. Last release is 4.0.0, but with 3.3.3 my problem was fixed.
For remove ws module just navigate to it (node_modules/ws) trought the filesystem and delete it. After that, open your Command Line Interface and type npm install --save ws@3.3.3, or just npm install ws if your packaje.json have the right configuration for ws package.