IƱaki Baz Castillo wrote:
In your case I'd use:
sl_send_reply("100", "Call Going To PSTN");
but obviously this is pure SIP, nothing says that your VoIP client will display the reason of a "100" reply.
Exactly. There is nothing in the SIP specification(s) that says: If you send a message with this reason code and body, a "VoIP client" (what do you mean by that, exactly? A UAC?) will somehow "display" it. That is entirely an application-specific matter. Some clients doubtless implement this over a NOTIFY transport or what have you, but otherwise, that's not specified.