Doesn't work with some servers

[AlexKMDev]

For example google ones:

stun.l.google.com:19302
stun1.l.google.com:19302
stun2.l.google.com:19302
stun3.l.google.com:19302
stun4.l.google.com:19302

Test1 fails with "No changed address." error. Any idea what could be wrong?

[chrikoch]

I'm still getting the error "Server error: no changed address." using the google servers.

EDIT: Google servers seem to have changed their port. But when using Port 19305 the returned *Host is nil.

[xiang90]

@chrikoch Can you please provide a reproduce step?

[chrikoch]

@xiang90

My Code:

func minimalExample() {
stunClient := stun.NewClient()
stunClient.SetServerHost("stun1.l.google.com", 19305)
_, host, err := stunClient.Discover()

if err != nil {
    log.Println(err)
    return
}

if host == nil {
    log.Println("no host")
    return
}

}

Output is:
2016/08/20 22:33:27 no host

[ccding]

I think there is a bug in the Google servers. In test2, we send a request to the server with flag of changing IP and port. But the received packet is from the original IP and port (not changed).

Let me know if you think it is not Google servers' bug and have any hints to me. Thanks.

[ccding]

Sorry I messed up this bug with another one. Please ignore the above comment. See below:

In the test1 response from Google servers, it doesn't provide a changedAddr attribute, which is required by RFC3489. I think this is a bug in Google servers. I think the previous fix is incorrect.

[chrikoch]

@ccding @xiang90
I tried to debug this a bit more. Now I think 19302 seems to be the correct port for googles stun servers. Requests to 19305 don't give any response in wireshark:

So it's even stranger the lib doesn't return an error but a nil host.

Requests to 19302 do get a response from google:

Output of my testing code is in that case:
2016/08/21 20:39:26 Server error: no changed address.

[ccding]

What I meant was that, the response doesn't include a CHANGED-ADDRESS field, which is required by RFC (see https://tools.ietf.org/html/rfc3489#section-11.2.3)

[chrikoch]

Actually I was looking for a stun library working with in-the-wild-servers, even if they don't respect the RFC ;-)

[ccding]

If a server doesn't follow RFC, how can I understand its response given the fact that the server itself doesn't provide any documentation? I'd suggest you to use this server stun.ekiga.net:3478

[ccding]

The reason RFC requires this filed is that we need this CHANGED-ADDRESS field to perform the next step test. If it doesn't exist, I cannot perform the next step. Therefore I have to report an error.

[xiang90]

@ccding @chrikoch I think we want to accept the patch if it makes go-stun more adoptive to the wild. However, the patch itself needs to be well documented and isolated to make it clear that it exists for the purpose of one wild deployed service.

@chrikoch Do you want to help on this? Thank you!