github.com/pebbe/zmq2 (2.2.0) sub socket cannot connect to github.com/go-zeromq/zmq4 pub socket

[Kimbsen]

As soon as the subscriber connects(subscribes) the pub socket server starts logging:

zmq4: could not open a ZMTP connection with "tcp://127.0.0.1:5000": zmq4: could not initialize ZMTP connection: zmq4: could not exchange greetings: zmq4: could not recv greeting: could not read ZMTP greeting: unexpected EOF

The subscriber does not report any error, but also receives no events

I think 2.2.0 should be compatible with zmq4, but i can't get it to work.
http://wiki.zeromq.org/area:faq#toc9

Or am i just incorrectly assuming this should work? :)

testclient for github.com/pebbe/zmq2

package main

import (
	"log"
	"os"
	"time"

	zmq "github.com/pebbe/zmq2"
)

func main() {

	const addr = "tcp://localhost:5000"

	socket, err := zmq.NewSocket(zmq.SUB)
	if err != nil {
		log.Fatal(err)
	}
	if err := socket.Connect(addr); err != nil {
		log.Fatal(err)
	}

	if err := socket.SetSubscribe(os.Args[1]); err != nil {
		log.Fatal(err)
	}

	poller := zmq.NewPoller()
	poller.Add(socket, zmq.POLLIN)

	for {
		sockets, err := poller.Poll(2 * time.Second)
		if err != nil {
			log.Fatal(err)
		} else {
			for _, socket := range sockets {
				data, err := socket.Socket.RecvBytes(0)
				if err != nil {
					log.Fatal(err)
				} else {
					log.Println("GOT", string(data))
				}
			}
		}
	}
}

testserver for github.com/go-zeromq/zmq4

package main

import (
	"context"
	"log"
	"os"
	"time"

	"github.com/go-zeromq/zmq4"
)

func main() {

	const addr = "tcp://localhost:5000"

	pub := zmq4.NewPub(context.Background())
	defer pub.Close()

	if err := pub.Listen(addr); err != nil {
		log.Fatal(err)
	}

	event := func() zmq4.Msg {
		return zmq4.NewMsgFrom([]byte(os.Args[1]), []byte("RANDOM_STRING"))
	}
	for {
		select {
		case <-time.After(1 * time.Second):
			if err := pub.Send(event()); err != nil {
				log.Fatal(err)
			} else {
				log.Println("SENT event")
			}
		}
	}
}

while a slightly modified example can connect and receive events fine:

package main

import (
	"context"
	"log"
	"os"

	"github.com/go-zeromq/zmq4"
)

func main() {
	log.SetPrefix("psenvsub: ")

	//  Prepare our subscriber
	sub := zmq4.NewSub(context.Background())
	defer sub.Close()

	err := sub.Dial("tcp://localhost:5000")
	if err != nil {
		log.Fatalf("could not dial: %v", err)
	}

	err = sub.SetOption(zmq4.OptionSubscribe, os.Args[1])
	if err != nil {
		log.Fatalf("could not subscribe: %v", err)
	}

	for {
		// Read envelope
		msg, err := sub.Recv()
		if err != nil {
			log.Fatalf("could not receive message: %v", err)
		}
		log.Printf("[%s] %s\n", msg.Frames[0], msg.Frames[1])
	}
}

[sbinet]

yeah, go-zeromq/zmq4 hasn't handling of the old ZMTP protocol(s) baked in.

• https://rfc.zeromq.org/spec/23/#detecting-zmtp-20-peers
• https://github.com/go-zeromq/zmq4/blob/v0.15.0/protocol.go#L90..L125

PRs welcomed :)

[Kimbsen]

Ah i see. Thanks for the quick reply!