<apex:form >
<apex:commandLink onclick="publishData2();" value="publish" reRender="dummy"/><br/>
<apex:outputPanel id="dummy"></apex:outputPanel>
<apex:outputPanel id="panel1" rendered="{!showCanvas2}">
    <div id="container1"></div>
<apex:canvasApp canvasId="mybox1canvas" containerId="container1" developerName="canvasappsdk" onCanvasAppLoad="publishData();"
    height="1000px" width="800px"
    parameters="{!jsonstStr4}"/> <!-- {!jsonstStr4} {p1:'value1',p2:'value2',p3:'value3'} -->
</apex:outputPanel>
    </apex:form>

console.log('in subscribe func on server '+data.value);
             Sfdc.canvas.byId('input2').innerHTML = 'Opportunities passed in publish :' +data.value;

         } });