10 min read
Introducing Darwvin Softphone: a SIP softphone that tells you why a call failed
Darwvin Softphone is a SIP softphone for Android and Linux, in Early Access. Its Call Doctor ranks the likely causes of a failed or bad-sounding call.
Troubleshooting
Posts about Troubleshooting, newest first.
14 min read
SIP and NAT explained: STUN, TURN, ICE, rport and SIP ALG
SIP NAT traversal explained: why NAT breaks SIP calls, how rport, STUN, TURN and ICE help, why SIP ALG hurts, and the Asterisk PJSIP settings.
13 min read
SIP response codes explained: the complete reference with causes and fixes
SIP response codes from 1xx to 6xx with RFC 3261 meanings, the real causes of 401, 403, 480, 488 and 503, and how to fix each one.
12 min read
Fix "Permission denied (publickey)" and "Host key verification failed"
Fix Permission denied (publickey) and Host key verification failed: read ssh -vvv output, check keys and permissions, sshd logs and known_hosts fingerprints.
11 min read
One-way audio or no audio on VoIP calls: causes and step-by-step fixes
Fix one-way or no audio on VoIP calls by checking SDP addresses, SIP ALG, blocked RTP ports, symmetric RTP, codecs and hold, with captures and Asterisk fixes.