Sample code for demonstrating device/agent communication with an Electric Imp (and round trip latency).

latency.agent.nut

function startTime(time)
{
    // Send the device a 'pong' message immediately
    
    device.send("pong", time);
}

// When we get a 'ping' message from the device, call start_time()

device.on("ping", startTime); 

latency.device.nut

function ping() 
{
    // Send a 'ping' message to the server with the current millis counter
    
    agent.send("ping", hardware.millis());
}

function returnFromImp(startMillis)
{
    // Handle a 'pong' message from the server

    // Get the current time
    
    local endMillis = hardware.millis();
    
    // Calculate how long the round trip took
    
    local diff = endMillis - startMillis;
    
    // Log it
    
    server.log("Round trip took: " + diff + "ms");
    
    // Wake up in 5 seconds and ping again
    
    imp.wakeup(5.0, ping);
}

// When we get a 'pong' message from the agent, call returnFromImp()

agent.on("pong", returnFromImp);

// Start the ping-pong

ping();