Sending a Message from a HTTP Client to a WebSocket Endpoint

The following sections walk you through a sample scenario that demonstrates how to send a message from a HTTP client to a WebSocket endpoint via WSO2 Enterprise Integrator:

Introduction

If you need to send a message from a HTTP client to a WebSocket endpoint via WSO2 Enterprise Integrator, you need to establish a persistent Websocket connection from WSO2 Enterprise Integrator to the WebSocket back-end.

To demonstrate this scenario, you need to create two dispatching sequences. One for the client to back-end mediation, and another for the back-end to client mediation. Then you need to create a proxy service to call the created sequences.

Prerequisites

• Start the WSO2 Enterprise Integrator. For information on how to start WSO2 Enterprise Integrator, see Running the Product.
• Download the sample netty artifacts.

• Execute the following command to start the WebSocket server on port 8082:

  java -cp netty-example-4.0.30.Final.jar:lib/*:. io.netty.example.http.websocketx.server.WebSocketServer

Configuring the sample scenario

• Create the sequence for client to back-end mediation as follows:

  <?xml version="1.0" encoding="UTF-8"?>
  <sequence name="dispatchSeq" xmlns="http://ws.apache.org/ns/synapse">
      <in>
          <property name="OUT_ONLY" value="true"/>
          <property name="FORCE_SC_ACCEPTED" scope="axis2" type="STRING" value="true"/>
          <property name="websocket.accept.contenType" scope="axis2" value="application/json"/>
          <send>
              <endpoint>
                  <address uri="ws://localhost:8082/websocket"/>
              </endpoint>
          </send>
      </in>
  </sequence>

• Create the sequence for the back-end to client mediation as follows:

  <sequence name="outDispatchSeq" xmlns="http://ws.apache.org/ns/synapse">
    <log level="full"/>
  </sequence>

• Create a proxy service as follows to call the above sequences:

  <?xml version="1.0" encoding="UTF-8"?>
  <proxy xmlns="http://ws.apache.org/ns/synapse"
         name="websocketProxy1"
         transports="http,https"
         statistics="disable"
         trace="disable"
         startOnLoad="true">
     <target inSequence="dispatchSeq" faultSequence="outDispatchSeq"/>
     <description/>
  </proxy>

Executing the sample scenario

Execute the following command to invoke the proxy service:

curl -v --request POST -d "<?xml version=\"1.0\" encoding=\"UTF-8\"?><soapenv:Envelope xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\"><soapenv:Body><test>Value</test></soapenv:Body></soapenv:Envelope>" -H Content-Type:"text/xml" http://localhost:8280/services/websocketProxy1

Analyzing the output

If you analyze the log, you will see that a HTTP request is sent to the WebSocket server, and that the WebSocket server injects the response to the out sequence.