How to Communicate between Frontend and Backend

[zx42]

Sorry for the rookie questions:

1. Is there a simple convenient way to transfer data from the front end (go-app code in browser) to the back end?
   • So far I have used REST requests to the back end http server but I was forced to run a second http service on another port because I could not add more http handlers for different URL paths on the main http service.
2. Is there a simple convenient way to stream data from the back end to the front end?
   • I assume a web socket might work.

[maxence-charriere]

Is there a simple convenient way to transfer data from the front end (go-app code in browser) to the back end? So far I have used rest requests to the back end http server but I was forced to run a second http service on another port

This is the correct way, just have to set up another HTTP handler:

func main() {
	app.Route("/", &hello{})
	app.Route("/hello", &hello{})
	app.RunWhenOnBrowser()


	http.Handle("/", &app.Handler{
		Name:        "Hello",
		Description: "An Hello World! example",
	})

	
	http.Handle("/api/", YOUR_HTTP_HANDLER) // <--------- standard go http

	if err := http.ListenAndServe(":8000", nil); err != nil {
		log.Fatal(err)
	}
}

[maxence-charriere]

Is there a simple convenient way to stream data from the back end to the front end? I assume a web socket might work.

Web socket in fact works. It pretty simple to implement with go => https://pkg.go.dev/golang.org/x/net/websocket

[pizzalord22]

I tried using websocket for communication but i keep getting the following error "Connection refused" when using the library other websocket clients work just fine, i also tried using the gorilla websocket library but using a different router then the default http library causes a lot of errors where files can't be found

[maxence-charriere]

Do you have some code to see what is happening? or log? if you got the connection refused with the WebSocket lib mentioned above, did you make sure that the WebSocket-Origin is set ?

[pizzalord22]

server:

return func(w http.ResponseWriter, r *http.Request) {
        log.Println("incoming request from:", r.RemoteAddr)
        connection, err := upgrader.Upgrade(w, r, nil)
        if err != nil {
            w.WriteHeader(http.StatusInternalServerError)
            _, _ = w.Write([]byte("Upgrade error: " + err.Error()))
            return
        }
        connection.WriteMessage(websocket.TextMessage, []byte("test message"))
        connection.WriteMessage(websocket.CloseMessage, []byte("test message"))
        connection.Close()
    }

client:

    var d websocket.Dialer
    d = websocket.Dialer{HandshakeTimeout: 30 * time.Second}
    connection, _, err := d.Dial("ws://server/ws", nil)
    if err != nil {
        log.Println("ws connection error: ", err)
    } else {
        msgType, msg, err := connection.ReadMessage()
        if err != nil {
            log.Println("read message error: ", err)
        }
        if msgType == websocket.CloseMessage {
            connection.Close()
        }
        log.Println("test value:", string(msg))
    }

[maxence-charriere]

What package are you using for websocket? Also look like the address in dial is not correct.

[pizzalord22]

i am using github.com/gorilla/websocket, i have remove the real ip, but i have tested it with an other client written in go and that one could connect and send / receive messages

[fbaube]

You might want to try nhooyr.io/websocket

[AdamRGrey]

@pizzalord22 I don't know if it's the issue you're facing, but gorilla/websocket doesn't support wasm. nhooyr.io/websocket does, though.

[oderwat]

I am using nhooyr.io/websocket too. With good success. But I think I want to switch to a package that has less dependencies as it adds quite a lot.

[maxence-charriere]

Did you guys tried the go one => https://pkg.go.dev/golang.org/x/net/websocket

i found it pretty well built and extensible and work well with standard http.

[fbaube]

I have had good results using github.com/dennwc/dom/net/ws in webassenbly.

[oderwat]

@maxence-charriere I actually wanted to try it next. It tells users to try the other packages but maybe it is just complete enough for what we need.

@fbaube This seems not to be maintained and the latest changes were 3 years ago. It also means that you need to include all the other "dom/js" related stuff which may be of use but to me, they are not in combination with go-app. I actually wonder why people are using any other js frontend (vite came up) or "manual js dom" together with go-app. To me, this looks like mixing jQuery with VueJS and native Javascript. Can work but why?