I had exactly the same problem. the plugin you have mentioned worked only for a HTTP-like request/response but I couldn't use it for a "long" connection.
Have a look at this http://github.com/maciejzaleski/JMeter
Features:
- Supports HTTS/HTTPS (ws/wss) version of the WebSocket protocol
- Option to ignore SSL certificate errors
- Streaming allows for a single connection to remain open for the duration of the test
- Response has to match predefined regular expression
- Response timeout
- Response message backlog (build the Sampler response from multiple server messages)
- Connection could be closed if server sends a message matching predefined regular expression