[doc] Please document how to handle websocket.NetConn().Read() return zero and nil

[bronze1man]

I just wrote a demo to test it. Here is my code:

package main

import (
	"net/http"
	"io"
	"fmt"
	"nhooyr.io/websocket"
	"context"
	"time"
	"strconv"
)

func main(){
	go func(){
		http.ListenAndServe(`127.0.0.1:9098`,echoServer{})
	}()
	time.Sleep(time.Millisecond*10)
	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
	defer cancel()
	c, _, err := websocket.Dial(ctx, `http://127.0.0.1:9098`, &websocket.DialOptions{
		Subprotocols: []string{"echo"},
	})
	defer c.Close(websocket.StatusNormalClosure,``)
	ctx = context.Background()
	inList:=[]byte{1}
	buf:=make([]byte,1024)
	c2:=websocket.NetConn(ctx,c,websocket.MessageBinary)
	for i:=0;i<10;i++{
		_,err=c2.Write(inList)
		if err!=nil{
			panic(err)
		}
		nr,err := c2.Read(buf)
		if err!=nil{
			panic(err)
		}
		if nr==0{
			panic(`nr==0 `+strconv.Itoa(i))
		}
	}
}

// echoServer is the WebSocket echo server implementation.
// It ensures the client speaks the echo subprotocol and
// only allows one message every 100ms with a 10 message burst.
type echoServer struct {
	// logf controls where logs are sent.
	logf func(f string, v ...interface{})
}

func (s echoServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	c, err := websocket.Accept(w, r, &websocket.AcceptOptions{
		Subprotocols: []string{"echo"},
	})
	if err != nil {
		s.logf("%v", err)
		return
	}
	defer c.Close(websocket.StatusInternalError, "the sky is falling")
	if c.Subprotocol() != "echo" {
		c.Close(websocket.StatusPolicyViolation, "client must speak the echo subprotocol")
		return
	}
	for {
		err = echo(r.Context(), c)
		if websocket.CloseStatus(err) == websocket.StatusNormalClosure {
			return
		}
		if err != nil {
			s.logf("failed to echo with %v: %v", r.RemoteAddr, err)
			return
		}
	}
}

// echo reads from the WebSocket connection and then writes
// the received message back to it.
// The entire function has 10s to complete.
func echo(ctx context.Context, c *websocket.Conn) error {
	ctx, cancel := context.WithTimeout(ctx, time.Second*10)
	defer cancel()

	typ, r, err := c.Reader(ctx)
	if err != nil {
		return err
	}

	w, err := c.Writer(ctx, typ)
	if err != nil {
		return err
	}

	_, err = io.Copy(w, r)
	if err != nil {
		return fmt.Errorf("failed to io.Copy: %w", err)
	}

	err = w.Close()
	return err
}

And I found that websocket.NetConn().Read() will return zero and nil .
I never seen a net.Conn object work like this.
I do not know how to do with it , skip? But I am afraid of unlimit loop...

[nhooyr]

#367

Yes you always have to check n, if n is zero you just keep going.