Fix invalid state error on DTMF send

[BlindChickens]

Sending a DTMF tone after a 183 Session Progress for example would raise an INVALID_STATE_ERROR. This PR fixes that.

[jmillan]

Hi,

Reverted due to this #689

[BlindChickens]

Hi, I cannot exactly deduce what extra conditions I need to test on. If you can clarify I can test.
What I can say is that before the change it does not work for me right after a 183 Session Progress, and after the change it works anytime from 183 Session Progress to 200 OK.

[jmillan]

I guess you are sending DTMFs of type JsSIP_C.DTMF_TRANSPORT.RFC2833, right?

[ibc]

Can I know more? It should indeed be possible to send DTMF (in band or via INFO) once we have received a 18X.

[jmillan]

Can I know more? It should indeed be possible to send DTMF (in band or via INFO) once we have received a 18X.

That's why I ask. I want to confirm this, because INFO DTMFs for sure don't work.

[ibc]

Why not?

[ibc]

It should be possible to send in-dialog messages as far as the dialog is created, and that happens once we get a 18X with Contact header.

[jmillan]

Due to the problem posted here #689. Yes, this is a bug in the library.

[ibc]

BTW I promise it's possible to send DTMF in PSTN calls even before the call is answered. I used that in the past.

[ibc]

Si I think such a bug must be fixed, yes, but no real reason to revert this PR.

[BlindChickens]

I guess you are sending DTMFs of type JsSIP_C.DTMF_TRANSPORT.RFC2833, right?

Yes indeed I am.

[BlindChickens]

If I send the DTMF of type INFO, there is no error on my side, but also no corresponding sound on the other end indicating that it worked. I don't know what the differences are here, but I am going to assume our service provider does not allow for the INFO type DTMF's. I can see the websocket messages going out when I send them, but no sound on the other end.

[jmillan]

Si I think such a bug must be fixed, yes, but no real reason to revert this PR.

That's a point.

We are now preventing RFC2833 DTMFs from being sent. Ok, let's merge it.

[jmillan]

Changes added to the new release.