SIP OPTIONS support with V20

[Wbenko]

We use a sip OPTIONS request as a heartbeat to tell if 3CX software is online, we don't use the OPTIONS request to query anything. There is this thread from 2019 where it looks like other people also do this, and that in previous versions of 3CX, the status was that 3CX would respond to SIP OPTIONS messages blindly with a 200 OK

Thread 'SIP OPTIONS Support'

Jul 22, 2019

Does anyone know the status for SIP OPTIONS support with 3CX. The below post is very old now but wanted to know if the situation was still the case:
https://www.3cx.com/community/threads/sip-option-message.2208/

Calls were failing up until the point of the provider (in their words) disabled SIP OPTIONS on their side (but have said the only want to do this as a temporary work around) until we investigate our side (3CX) as soon as this was configured however calls worked straight away.

The provider is un-supported as the customer is based in Hong Kong and they are doing some sort of...

• eddv123
• Replies: 1
• Forum: Phone System / PBX

This is the options request we use that has worked with 3CX pre V20 and the response we are getting.

OPTIONS sip:[3CX server IP] SIP/2.0
Via: SIP/2.0/TCP 0.0.0.0;branch=z9hG4bK;rport
Max-Forwards: 70
To: <sip:[3CX server IP]>
From: <sip:0.0.0.0>;transport=Tcp
Call-ID: MyHeartbeat
CSeq: 1 OPTIONS
Contact: <sip:0.0.0.0>
Content-Length: 0

SIP/2.0 400 Bad Request
Via: SIP/2.0/TCP 0.0.0.0;branch=z9hG4bK;rport=49624;received=[Our Servers IP]
To: <sip:[3CX server IP]>;tag=d952bc02
From: <sip:0.0.0.0>;transport=Tcp
Call-ID: MyHeartbeat
CSeq: 1 OPTIONS
Content-Length: 0

Are there any differences with how 3CX processes OPTIONS requests with version 20?
Is there any authentication that needs to take place before this request can be sent? Previously that isn't something we have had to do
Is there any additional logging in 3CX that would show us what is wrong with our request? Right now the bad request response is the only log we are seeing with no indication of what is wrong with our request.
Would anyone be able to provide us with a network capture of any OPTIONS request and response from 3CX in V20 that we could use to compare with how we send our request?