Hello,

I believe , your invite needs to be formatted like a typical SIP URI;

sip:<extension>@<ip_address>

http://www.voip-info.org/wiki/view/SIP+URI

1285616672.1717 DEBUG:<2>       REQ  INVITE sip:2145555555@192.168.1.2
+54 with body
1285616672.1753 DEBUG:<2> Net::SIP::Leg::receive[421]: received on 192
+.168.1.254:42508 from 192.168.1.254:5060 packet
[download]

Your asterisk has to either have an extension built for the address / phone number in sip.conf and extensions.conf or your registered agent must have access to your outbound context in extensions.conf and match a extension;  exten => _1NXXNXXXXXX

UPDATE: I tested your code and it works, correcting the URI. Also, the extension does not have to be _1NXX.... it just has to match your dialing pattern.