Without code to reproduce this (ideally a minimal reproduction), it is extremely difficult to diagnose what is going on. Do you have an example client/server setup you could provide? Perhaps this would also be more appropriate for hashicorp/mdns#80 and once you’ve determined it’s an issue with the Go toolchain, you could then revisit this issue.

package main

import (
        "fmt"
        "github.com/hashicorp/mdns"
)

func main() {
        // Make a channel for results and start listening
        fmt.Println("searching for new entries")
        entriesCh := make(chan *mdns.ServiceEntry, 4)
        go func() {
                for entry := range entriesCh {
                        fmt.Printf("Got new entry: %v\n", entry)
                }
        }()

        // Start the lookup
        mdns.Lookup("_ssh._tcp", entriesCh)
        close(entriesCh)
}

Please see the call stack for verification of the Golang toolchain.

Does this work as expected on platforms other than Windows?

yeah, works great on a Pi. see attachment.

Thanks. That’s helpful.

Can you attach text instead of images, please? Images are harder to read and hurt accessibility.

@mikioh @alexbrainman

Sure. Will do.

Tentatively marking this a release blocker for 1.15 while we gather more info.

Could be due to one of the known bugs listed here: https://golang.org/pkg/net/#pkg-note-BUG

Just wanted to note I've updated Go (same problem, however)

go version go1.14.1 windows/amd64

Any updates on this or any potential workarounds?

@jmarkel44 it’s been two days. Please be patient.

I don't understand the test program, as it doesn't wait for the goroutine to complete. What happens if you use a sync.WaitGroup or some such thing to ensure that your program doesn't exit before the goroutine finishes running?

There's a Timeout in the Lookup function. The code above is the recommended way to use the library too, based on github.com/hashicorp/mdns.

As noted, this works perfectly on a RPi.

Thanks.

I'm sure you're right, but when I look at that program it looks clearly incorrect. Humor me. Thanks.

What results are you getting when running the program?

I don't have a Windows system.

But on my GNU/Linux system I get

searching for new entries
2020/04/03 13:09:02 [INFO] mdns: Closing client {0xc000010030 0xc000010038 0xc000010040 0xc000010048 1 0xc0000181e0}

so if you do something like

$ dns-sd -B _workstation._tcp

are there any mDNS devices on the network?

I don't have dns-sd installed.

It would not surprise me if there are no mDNS devices on the network.

@jmarkel44

I never used this package github.com/hashicorp/mdns - I don't know what it does. But I tried running your program on Linux:

searching for new entries
2020/04/05 16:52:10 [INFO] mdns: Closing client {0xc000010030 0xc000010038 0xc000010040 0xc000010048 true 0xc000068180 {1 0}}
2020/04/05 16:52:10 [ERR] mdns: Failed to read packet: read udp4 0.0.0.0:55783: use of closed network connection

and on Windows

searching for new entries
2020/04/05 16:54:47 [ERR] mdns: Failed to bind to udp6 port: listen udp6 [ff02::fb]:5353: setsockopt: not supported by windows
2020/04/05 16:54:48 [INFO] mdns: Closing client {0xc00014c020 0xc00014c028 0xc00014c030 <nil> true 0xc000108180 {1 0}}
2020/04/05 16:54:48 [ERR] mdns: Failed to read packet: read udp4 0.0.0.0:54096: use of closed network connection

And 2 outputs looks very similar to me.

If you think the problem is in UDPConn.WriteToUDP, please, create small program that we can run on our computers to investigate. Do not assume we have Wireshark installed or other special tools available.

Thank you.

Alex

So this came down to a set-interface issue on the windows platform. traversing the entire list of possible interfaces resolves the issue we were seeing with mdns package.

Thanks for the help!

Closing the ticket.

So this came down to a set-interface issue on the windows platform. traversing the entire list of possible interfaces resolves the issue we were seeing with mdns package.

Thanks for the help!

Closing the ticket.

Please, could you provide a code example of the solution?