I am trying to implement a simple "global" counter that updates based on every user that clicks the button on their browsers button. For example, if you go to the website and click the button, I will see the counter increase on my side if I'm on the same website. I sought to do this with long polling, but am facing some issues. Mainly the server variable is not coming back as I think it should.
The server:
package main
import (
"net/http"
"log"
"io"
"io/ioutil"
)
var messages chan string = make(chan string, 100)
var counter = 0
func PushHandler(w http.ResponseWriter, req *http.Request) {
body, err := ioutil.ReadAll(req.Body)
if err != nil {
w.WriteHeader(400)
}
counter += 1
messages <- string(counter)
}
func PollResponse(w http.ResponseWriter, req *http.Request) {
io.WriteString(w, <-messages)
}
func main() {
http.Handle("/", http.FileServer(http.Dir("./")))
http.HandleFunc("/poll", PollResponse)
http.HandleFunc("/push", PushHandler)
err := http.ListenAndServe(":8005", nil)
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
The client:
<html>
<script language=javascript>
function longpoll(url, callback) {
var req = new XMLHttpRequest ();
req.open ('GET', url, true);
req.onreadystatechange = function (aEvt) {
if (req.readyState == 4) {
if (req.status == 200) {
callback(req.responseText);
longpoll(url, callback);
} else {
alert ("long-poll connection lost");
}
}
};
req.send(null);
}
function recv(msg) {
var box = document.getElementById("counter");
box.value += msg + "
";
}
function send() {
var box = document.getElementById("counter");
var req = new XMLHttpRequest ();
req.open ('POST', "/push?rcpt=", true);
req.onreadystatechange = function (aEvt) {
if (req.readyState == 4) {
if (req.status == 200) {
} else {
alert ("failed to send!");
}
}
};
req.send("hi")
//box.innerHTML += "test" ;
}
</script>
<body onload="longpoll('/poll', recv);">
<h1> Long-Poll Chat Demo </h1>
<p id="counter"></p>
<button onclick="send()" id="test">Test Button</button>
</body>
</html>
The counter variable is not coming back from the server for some reason. I believe I am changing the state every time the button is clicked and so the longpolling function should get the newly updated counter variable. If you have any suggestions, please let me know!
