I have a large number (50+) Sangoma desktop apps on this deployment. Everything module is up to date from Stable rep and Debian is fully updated. Apps are running the latest version, 4.2.0.
Apps will randomly become unreachable, then reachable again sometimes (other times they have to be manually reconnected). I turned sip debug on and I’m seeing normal looking sip options traffic to and from these apps WHILE asterisk shows they are Unavailable. Here is an example check in from an app that is responded to by the PBX
[2026-01-21 14:45:01] VERBOSE[183725] res_pjsip_logger.c: <— Received SIP request (786 bytes) from WS:127.0.0.1:44348 —>
OPTIONS sip:[email protected]:6443 SIP/2.0^M
Via: SIP/2.0/WSS 5jl9marrq5ig.invalid;branch=z9hG4bK3075457^M
Max-Forwards: 69^M
To: sip:[email protected]:6443^M
From: sip:[email protected]:6443;tag=f3e99pmits^M
Call-ID: jaoii0ubhaj3cd7fgova^M
CSeq: 6838 OPTIONS^M
Authorization: Digest algorithm=MD5, username=“98182”, realm=“asterisk”, nonce=“1769024701/ba2f76dad18ded45aa13a7912d05fb20”, uri=“sip:[email protected]:6443”, response=“5c20bc4db570535ea701ad38f693a54a”, opaque=“2b4fa6216ab47e31”, qop=auth, cnonce=“v87d0ua45rlk”, nc=00000001^M
Content-Type: application/sdp^M
Allow: INVITE,ACK,CANCEL,BYE,UPDATE,MESSAGE,OPTIONS,REFER,INFO,NOTIFY^M
Supported: outbound^M
User-Agent: Sangoma Windows Softphone 4.2.0^M
Content-Length: 0^M
[2026-01-21 14:45:01] VERBOSE[183725] res_pjsip_logger.c: <— Transmitting SIP response (826 bytes) to WS:127.0.0.1:44348 —>
SIP/2.0 200 OK^M
Via: SIP/2.0/WSS 5jl9marrq5ig.invalid;rport=44348;received=127.0.0.1;branch=z9hG4bK3075457^M
Call-ID: jaoii0ubhaj3cd7fgova^M
From: sip:[email protected];tag=f3e99pmits^M
To: sip:[email protected];tag=z9hG4bK3075457^M
CSeq: 6838 OPTIONS^M
Accept: application/sdp, application/xpidf+xml, application/cpim-pidf+xml, application/pidf+xml, application/dialog-info+xml, application/simple-message-summary, application/simple-message-summary, application/pidf+xml, application/dialog-info+xml, message/sipfrag;version=2.0^M
Allow: OPTIONS, INVITE, ACK, BYE, CANCEL, UPDATE, PRACK, REGISTER, SUBSCRIBE, NOTIFY, PUBLISH, MESSAGE, INFO, REFER^M
Supported: 100rel, timer, replaces, norefersub^M
Accept-Encoding: identity^M
Accept-Language: en^M
Server: FPBX-17.0.24(22.7.0)^M
Content-Length: 0^M
The Sangoma desktop app logs show a “503 service unavailable” response from the PBX but I don’t see any corresponding errors in the asterisk log or rtapi log:
error [2026-01-21T17:34:09.837Z]: Failed to receive the response of SIP OPTIONS heartbeat message from SIP server - CAUSE: SIP Failure Code. Not reloading app, continuing with the process
error [2026-01-21T17:34:09.838Z]: {
originator: ‘remote’,
response: {
data: ‘SIP/2.0 503 Service Unavailable\r\n’ +
‘Via: SIP/2.0/WSS ag689gor6u5h.invalid;rport;received=127.0.0.1;branch=z9hG4bK7038036\r\n’ +
‘Call-ID: 27gjoeqrl2235c1flu1r\r\n’ +
‘From: sip:[email protected];tag=e2k77cbchr\r\n’ +
‘To: sip:[email protected];tag=z9hG4bK7038036\r\n’ +
‘CSeq: 7552 OPTIONS\r\n’ +
‘Server: FPBX-17.0.24(22.5.2)\r\n’ +
‘Content-Length: 0\r\n’ +
‘\r\n’,
headers: {
Via: [
{
raw: ‘SIP/2.0/WSS ag689gor6u5h.invalid;rport;received=127.0.0.1;branch=z9hG4bK7038036’,
parsed: {
protocol: ‘SIP’,
transport: ‘WSS’,
host_type: ‘IPv4’,
host: ‘ag689gor6u5h.invalid’,
received: ‘127.0.0.1’,
branch: ‘z9hG4bK7038036’
}
}
],
‘Call-ID’: [
{ raw: ‘27gjoeqrl2235c1flu1r’, parsed: ‘27gjoeqrl2235c1flu1r’ }
],
From: [
{
raw: ‘sip:[email protected];tag=e2k77cbchr’,
parsed: { _uri: [Object], _parameters: [Object] }
}
],
To: [
{
raw: ‘sip:[email protected];tag=z9hG4bK7038036’,
parsed: { _uri: [Object], _parameters: [Object] }
}
],
CSeq: [
{
raw: ‘7552 OPTIONS’,
parsed: { value: 7552, method: ‘OPTIONS’ }
}
],
Server: [ { raw: ‘FPBX-17.0.24(22.5.2)’ } ],
‘Content-Length’: [ { raw: ‘0’, parsed: 0 } ]
},
method: ‘OPTIONS’,
via_branch: ‘z9hG4bK7038036’,
call_id: ‘27gjoeqrl2235c1flu1r’,
cseq: 7552,
from_tag: ‘e2k77cbchr’,
to_tag: ‘z9hG4bK7038036’,
body: ‘’,
sdp: null,
status_code: 503,
reason_phrase: ‘Service Unavailable’
},
cause: ‘SIP Failure Code’
}
It is happening across multiple locations all with different to no firewalls.
I’m completely lost on this one.