Link in your question looks to be not for jmeter plugin but for proxying module for Apache http server.
Correct link seems to be https://github.com/kawasima/jmeter-websocket - jmeter plugin for WebSocket protocol.
To use it you have to:
- download project sources;
- build ApacheJMeter_WebSocket.jar using maven;
- place jar into
$JMETER_HOME/lib/ext/ dir.
Jar files successfully built from sources using maven 3.0 (mvn validate compile package):
- ApacheJmeter_websocket-0.1.0-SNAPSHOT.jar
- ApacheJmeter_websocket-dist-0.1.0-SNAPSHOT.jar - with dependencies.
WebSocket Sampler available in the list of Samplers:
