Apache Karaf Websocket example


This example show how to register a websocket in the Karaf HTTP Service.


  • karaf-websocket-example is the main bundle using @WebSocket annotation.


The build uses Apache Maven. Simply use:

mvn clean install


On a running Karaf instance, first, you have to install the http, jetty and scr features:

karaf@root()> feature:install http
karaf@root()> feature:inistal jetty
karaf@root()> feature:install scr

Then, you can install the websocket example bundle:

karaf@root()> bundle:install -s mvn:org.apache.karaf.examples/karaf-websocket-example/LATEST

You can see the websocket registered in the HTTP service:

karaf@root()> http:list
ID │ Servlet                 │ Servlet-Name   │ State       │ Alias              │ Url
92 │ WebsocketExampleServlet │ ServletModel-2 │ Deployed    │ /example-websocket │ [/example-websocket/*]


The websocket is available on http://localhost:8181/example-websocket.

You can now register your client (like curl) on this URL:

curl --include \
     --no-buffer \
     --header "Connection: Upgrade" \
     --header "Upgrade: websocket" \
     --header "Host: localhost:8181" \
     --header "Origin: http://localhost:8181/example-websocket" \
     --header "Sec-WebSocket-Key: SGVsbG8sIHdvcmxkIQ==" \
     --header "Sec-WebSocket-Version: 13" \

Your client will have a Hello World message on your client every second.