Long Polling Agent HTTP Request Recipe

longpoll.agent.nut

// Set up outgoing request object as a global (we may need to cancel it, so we need a reference to it)

request <- http.get(webServiceURL, webServiceHeaders)

// Define the response handler

function handleResponse(responseTable)
{
    // Called when the imp receives an immediate acknowledgement from the remote service
    
    if (responseTable.statuscode == 200)
    {
        // Remote service has responded with 'OK' so decode
        // the response's body 'responseTable.body' and headers 'responseTable.headers'
        // Code omitted for clarity 
    }
    else
    {
        // Log an error
        
        server.log("Error response: " + responseTable.statuscode)
        
        // And cancel the request (since the remote server clearly can't fulfil the push request)
        
        request.cancel()
    }
}


// Define the long-poll response handler

function handleLongResponse(responseTable)
{
    // Called when the imp receives a long-term response from the remote service
    // This might be information 'pushed' to the device, so we need to re-submit
    // the request in order to receive future notifications
    
    if (responseTable.statuscode == 200)
    {
        // Remote service has responded with 'OK' so decode
        // the response's body 'responseTable.body' and headers 'responseTable.headers'
        // Code omitted for clarity
    }
    else
    {
        // Log an error
        
        server.log("Error response: " + responseTable.statuscode)
    }
    
    // Re-submit the long-poll request. We must initialize a new request for this
        
    request = http.get(webServiceURL, webServiceHeaders)
    request.sendasync(handleResponse, handleLongResponse)
}

// Send the request asynchronously. This will not block the imp CPU

request.sendasync(handleResponse, handleLongResponse)