knox-site/docs/websocket-support.md

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## WebSocket Support ##

### Introduction

WebSocket is a communication protocol that allows full duplex communication over a single TCP connection.
Knox provides out-of-the-box support for the WebSocket protocol, currently only text messages are supported.

### Configuration ###

By default WebSocket functionality is disabled, it can be easily enabled by changing the `gateway.websocket.feature.enabled` property to `true` in `<KNOX-HOME>/conf/gateway-site.xml` file.  

      <property>
          <name>gateway.websocket.feature.enabled</name>
          <value>true</value>
          <description>Enable/Disable websocket feature.</description>
      </property>

Service and rewrite rules need to changed accordingly to match the appropriate websocket context.

### Example ###

In the following sample configuration we assume that the backend WebSocket URL is ws://myhost:9999/ws. And 'gateway.websocket.feature.enabled' property is set to 'true' as shown above.

#### rewrite ####

Example code snippet from `<KNOX-HOME>/data/services/{myservice}/{version}/rewrite.xml` where myservice = websocket and version = 0.6.0

      <rules>
        <rule dir="IN" name="WEBSOCKET/ws/inbound" pattern="*://*:*/**/ws">
          <rewrite template="{$serviceUrl[WEBSOCKET]}/ws"/>
        </rule>
      </rules>

#### service ####

Example code snippet from `<KNOX-HOME>/data/services/{myservice}/{version}/service.xml` where myservice = websocket and version = 0.6.0

      <service role="WEBSOCKET" name="websocket" version="0.6.0">
        <policies>
              <policy role="webappsec"/>
              <policy role="authentication" name="Anonymous"/>
              <policy role="rewrite"/>
              <policy role="authorization"/>
        </policies>
        <routes>
          <route path="/ws">
              <rewrite apply="WEBSOCKET/ws/inbound" to="request.url"/>
          </route>
        </routes>
      </service>

#### topology ####

Finally, update the topology file at `<KNOX-HOME>/conf/{topology}.xml`  with the backend service URL

      <service>
          <role>WEBSOCKET</role>
          <url>ws://myhost:9999/ws</url>
      </service>