Is it possible to broadcast a WS response from a HTTPS endpoint?🤔

[marcelo-tm]

Hello everyone, I'm starting with websockets and I would like to know if it is possible to send a WS notification after some action is done inside a HTTPS endpoint. For example, I want to notify some users (I still need to figure out how to broadcast just to some users) when a new User is created on the admin panel. A POST request is made to the endpoint /agent and I would like to use websockets to send this new data and populate a data grid when a certain user is on the Agents creation screen.

I don't know if its clear, but is it possible to be made?

Thanks in advance.

[welcome]

Thanks for opening your first issue here! 🎉 Be sure to follow the issue template!

[WLun001]

Hi @maverickVision, I think you need separate websocket for that. And your API server connects to your websocket

app.Get("/operation", func (c *fiber.Ctx) error {

ws.send('message')

return c.SendString("done!")
})

[marcelo-tm]

Hi @WLun001, I've created this simple repo with the minimal working structure using fiber and it's websockets plugin, could you help me modify it to get it working?

https://github.com/maverickVision/testws

[WLun001]

@maverickVision I am not free at the moment, maybe you could take a look at this repo that address the same issue.

Checkout on problem branch.

[marcelo-tm]

Thanks @WLun001, I'll take a look. But I already saw that you are using the gin framework. Since I'm still beggining with Go, do you think it's better to learn gin instead of fiber?

[Fenny]

I'm not sure if I fully understand the question, but are you trying to run a websocket server with TLS?

package main

import (
	"crypto/tls"
	"log"

	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/websocket/v2"
)

func main() {
	// Fiber instance
	app := fiber.New()

	// Websocket upgrade
	app.Get("/ws", websocket.New(func(c *websocket.Conn) {
		var (
			mt  int
			msg []byte
			err error
		)
		for {
			if mt, msg, err = c.ReadMessage(); err != nil {
				log.Println("read:", err)
				break
			}
			log.Printf("recv: %s", msg)

			if err = c.WriteMessage(mt, msg); err != nil {
				log.Println("write:", err)
				break
			}
		}
	}))

	// Load tls certificate
	cer, err := tls.LoadX509KeyPair("./certs/ssl.cert", "./certs/ssl.key")
	if err != nil {
		log.Fatal(err)
	}

	config := &tls.Config{Certificates: []tls.Certificate{cer}}

	// Create custom listener
	ln, err := tls.Listen("tcp", ":443", config)
	if err != nil {
		panic(err)
	}

	// Access the websocket server: wss://localhost:443/ws
	// https://www.websocket.org/echo.html
	log.Fatal(app.Listener(ln))
}

[WLun001]

Thanks @WLun001, I'll take a look. But I already saw that you are using the gin framework. Since I'm still beggining with Go, do you think it's better to learn gin instead of fiber?

@maverickVision If you coming from Express, Fiber would be good choice, it has familiar APIs. Any framework will do, or without framework. That's my personal opinion.

[marcelo-tm]

@maverickVision I am not free at the moment, maybe you could take a look at this repo that address the same issue.

Checkout on problem branch.

@WLun001 I'm following your code from this repo, on the solution brach. The problem with fiber is that I can't access the responseWriter from fiber Context, in order to upgrade the connection inside the ServeWs method... and according to this issue #721, it is really not possible. I guess I will need to rewrite my project with Gin just because of this issue.

[WLun001]

@maverickVision You don't need to access to responseWriter. You could use https://github.com/gofiber/websocket.

[marcelo-tm]

@maverickVision You don't need to access to responseWriter. You could use https://github.com/gofiber/websocket.

I've made the following changes:

main.go

app.Get("/ws", websocket.New(func(c *websocket.Conn) {
		ws.ServeWs(hub, c, nc, subject)
	}))

ws.go

func ServeWs(hub *Hub, conn *websocket.Conn, nc *nats.Conn, subject string) {
	client := &Client{hub: hub, conn: conn, send: make(chan []byte, 256)}

	// subscribe nats
	sub, err := nc.Subscribe(subject, func(m *nats.Msg) {
		log.Println(string(m.Data))
		client.hub.broadcast <- m.Data
	})
	if err != nil {
		log.Fatal(err)
	}
	nc.Flush()

	if err := nc.LastError(); err != nil {
		log.Fatal(err)
	}

	client.natsSub = sub
	client.hub.register <- client

	// Allow Connection of memory referenced by the calloer by doing all work in new goroutines
	go client.writePump()
	go client.readPump()
}

I've switched the conn variable from the upgraded gin context to fiber websocket conn. All services gone up without issues (using the same commands you use in your code), but when I open a browser tab on localhost:8080, I get the following error on the make start-api console log:

2020/10/12 13:53:44 ws.go:64: Current connected ws client: 1
2020/10/12 13:53:44 ws.go:71: Unsubscribe
2020/10/12 13:53:44 ws.go:74: Current connected ws client: 0
panic: runtime error: invalid memory address or nil pointer dereference
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x149e03e]

goroutine 8 [running]:
github.com/fasthttp/websocket.(*Conn).Close(...)
	/Users/marcelo/go/pkg/mod/github.com/fasthttp/websocket@v1.4.3-beta.2/conn.go:344
github.com/maverickvision/testws/internal/ws.(*Client).writePump.func1(0xc00007e320, 0xc00028a0a0)
	/Users/marcelo/playground/golang/testws/internal/ws/ws.go:160 +0x3e
panic(0x150bc00, 0x1a06520)
	/usr/local/go/src/runtime/panic.go:969 +0x166
github.com/fasthttp/websocket.(*Conn).SetWriteDeadline(...)
	/Users/marcelo/go/pkg/mod/github.com/fasthttp/websocket@v1.4.3-beta.2/conn.go:781
github.com/maverickvision/testws/internal/ws.(*Client).writePump(0xc00028a0a0)
	/Users/marcelo/playground/golang/testws/internal/ws/ws.go:166 +0x311
created by github.com/maverickvision/testws/internal/ws.ServeWs
	/Users/marcelo/playground/golang/testws/internal/ws/ws.go:221 +0x240

I printed the conn and client variables on ws.go, and they are not null, what could it be?

I've updated my repo with the latest code, if you can help.

[WLun001]

@maverickVision I created a simplified example,using websocket in Fiber. You may take a look at this repo

[Fenny]

Closing due to inactivity, feel free to re-open.