client.html

<img id="camera" src="/img">
<script>
    speed = 0
    const setSpeed = (val) => {
        if (val != speed){
            var xhttp = new XMLHttpRequest();
            xhttp.open('POST', '/setSpeed?speed='+val, true);
            xhttp.send();
        }
        speed = val
    }

    const turn = (val) => {
        
    }

    window.onload = function() {
        var image = document.getElementById("camera");

        function updateImage() {
            image.src = image.src.split("?")[0] + "?" + new Date().getTime();

        }

        setInterval(updateImage, 1000);
    }

    document.addEventListener('keydown', (e)=>{
        c = e.code;
        if (c=='KeyW'){
            setSpeed(1);
        }
        if (c=='KeyS'){
            setSpeed(-1);
        }
    })

    document.addEventListener('keyup', (e)=>{
        setSpeed(0)
    })
</script>