Client.Ping method raises network disconnection: "use of closed network connection"

[lufia]

STEPS TO REPRODUCE

$ cd $GOPATH/src/github.com/surgemq/surgemq/examples/surgemq
$ go run *.go

then, go run this code with -logtostderr -vv 3:

package main

import (
    "flag"
    "log"

    "github.com/surgemq/message"
    "github.com/surgemq/surgemq/service"
)

func main() {
    flag.Parse()
    c := &service.Client{}
    cmsg := message.NewConnectMessage()
    cmsg.SetVersion(4)
    cmsg.SetCleanSession(true)
    cmsg.SetKeepAlive(10)
    if err := c.Connect("tcp://localhost:1883", cmsg); err != nil {
        log.Fatalln("Connect:", err)
    }

    fn := func(msg, ack message.Message, err error) error {
        log.Println("Pong:", err)
        return err
    }
    done := make(chan struct{})
    if err := c.Ping(service.OnCompleteFunc(fn)); err != nil {
        log.Fatalln("Ping:", err)
        close(done)
    }
    <-done
}

RESULTS

I1204 23:16:44.348778   13936 sendrecv.go:103/sender] (1/) Starting sender
I1204 23:16:44.348781   13936 process.go:46/processor] (1/) Starting processor
I1204 23:16:44.348883   13936 sendrecv.go:58/receiver] (1/) Starting receiver
I1204 23:16:44.349183   13936 service.go:210/stop] (1/) closing this.conn
I1204 23:16:44.349223   13936 sendrecv.go:100/func1] (1/) Stopping sender
E1204 23:16:44.349252   13936 sendrecv.go:76/receiver] (1/) error reading from connection: read tcp [::1]:61472->[::1]:1883: use of closed network connection
I1204 23:16:44.349364   13936 sendrecv.go:55/func1] (1/) Stopping receiver
I1204 23:16:44.349375   13936 service.go:220/stop] (1/) Received 16 bytes in 2 messages.
I1204 23:16:44.349383   13936 service.go:221/stop] (1/) Sent 6 bytes in 2 messages.

REASONS

In case of Client.Ping(), ackmsg.Msgbuf is empty in service.processAcked().
As a result, msg.Decode(ackmsg.Msgbuf) panics with "slice bounds out of range".

[ankoh]

Yep I saw that as well a while ago in your code. The problem is, that a closing socket does NOT return EOF but *net.OpError.

More information can be found here:
http://comments.gmane.org/gmane.comp.lang.go.general/76607

I decided to go for this dirty hack that was proposed in the googlegroups:

func IsEOF(err error) bool {
    if err == nil {
        return false
    } else if err == io.EOF {
        return true
    } else if oerr, ok := err.(*net.OpError); ok {
        if oerr.Err.Error() == "use of closed network connection" {
            return true
        }
    } else {
        if err.Error() == "use of closed network connection" {
            return true
        }
    }
    return false
}

[jcw]

+1

Same issue here, and the IsEOF mentioned above fixes it for me as well. I changed 2 cases in sendRecv.go and 2 more in process.go - from what I can tell, the current surgemq HEAD won't work without this workaround (this is on Mac OSX 10.11.2 with Go 1.5.3, FWIW).

[zhenjl]

Thanks @jcw @ankoh ... Would either of you be willing to submit a PR?

[godblesshugh]

here is a discussion for that error: errClosing.
and maybe
oerr, ok := err.(*net.OpError)
is not necessary, just need
if err.Error() == "use of closed network connection" { return true }
as @ankoh said.

[godblesshugh]

sorry.
if err.Error() == "use of closed network connection" { return true }
is not necessary, need
oerr, ok := err.(*net.OpError)

[lufia]

Unfortunately this repo is labeled as Unmaintained. I will reopen the issue if the status comes back to Maintained.