Thanks — I can help you check whether your local SIP server is configured correctly. Below are clear, practical checks you can run (network, TLS/certificates, signaling, and functional tests). Tell me which OS or SIP server software you’re using (e.g., Asterisk, FreeSWITCH, Kamailio, OpenSIPS) and whether you use TLS/SIPS so I can tailor commands. 1) Test TLS connectivity (if using TLS/SIPS) • Run:

openssl s_client -connect <http://your-sip-server.com:5061|your-sip-server.com:5061> -servername <http://your-sip-server.com|your-sip-server.com>

• A successful TLS handshake shows ServerHello and the server certificate. If it fails, note the error (hostname mismatch, expired cert, handshake failure). 2) Check certificate details • In the OpenSSL output confirm: ◦ Certificate CN or SAN matches the SIP domain. ◦ Certificate is not expired. ◦ The full certificate chain (intermediates) is present. Missing intermediates often cause clients to reject the cert. 3) Verify transport configuration • Confirm whether you intend to use

sips:

(TLS required for the whole route) or

sip:

with

transport=tls

(TLS for the next hop). Ensure your SIP endpoints and proxies advertise the correct transport (e.g.,

SIP/2.0/TLS

in Via headers). 4) Capture and inspect traffic • Capture packets while connecting:

sudo tcpdump -i eth0 -w sip-test.pcap port 5061

• Open the capture in Wireshark and check: ◦ TLS ClientHello/ServerHello and certificate exchange. ◦ Any TLS alert messages. ◦ SIP messages (if not encrypted) showing proper responses. 5) Inspect SIP headers for secure transport • When TLS is used, SIP headers should reflect it. Example

Via

header:

Via: SIP/2.0/TLS <http://client.example.com:5061;branch=z9hG4bK|client.example.com:5061;branch=z9hG4bK>...

• Ensure Record-Route and Contact headers are correct for your topology. 6) Functional SIP signaling tests • Send a test INVITE (from a SIP client or

sipp

) and observe server responses: ◦ Expected sequence:

100 Trying

→

180 Ringing

→

200 OK

(or appropriate error codes if misconfigured). • Example using sipp for a basic INVITE test: ◦ If you want, I can provide a sample

sipp

command tailored to your domain/port. 7) Common issues to check • Missing intermediate certificates in server chain. • TLS protocol or cipher mismatches (ensure TLS 1.2+ where required). • SNI misconfiguration if multiple domains share an IP. • Port or firewall blocking (5060/5061 or custom ports). If you want, I can: • Provide exact commands for your server software (Asterisk/FreeSWITCH/Kamailio/OpenSIPS). • Give a sample

sipp

scenario to run an INVITE test. • Help interpret OpenSSL or tcpdump/Wireshark output if you paste the errors or relevant snippets. Which SIP server software and transport (TLS or plain UDP/TCP) are you using? Sources: Understanding TLS in SIP | LiveKit