> The core idea behind SIP is good but unfortunately there
> are too many (telco!) parties involved, which making the
> specification unnecessary complex.
SIP is being developed in IETF (where HTTP was also developed). The fact that there is involvement of people from telco background/companies is a very good thing, because the lessons learnt and patterns discovered of over 100 years of telephony will not be lost.
Having said that both IETF and Java Specifications for SIP are striving for open standards and open APIs that easy to use and lower the entry barrier for developers.
> developers will always use the 'simplest solution that
> could possibly work' spells trouble for the future of SIP.
If you can understand -
public class MyHttpServlet extends HttpServlet {
private PrintWriter out = null;
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException {
response.setContentType("text/html");
out = response.getWriter();
// write the HTML header
out.println("<html>Hello</html>");
}
}
Then you can certainly understand the following SIP Servlet snippet.
public class MySipServlet extends SipServlet {
public void doInvite(SipServletRequest req)
throws IOException {
req.createResponse(180).send();
req.createResponse(200).send();
}
}
Where "INVITE" is one of the SIP messages like "GET" is for HTTP.
> For many problems there are alternative technologies that
> could be used (xmpp, twitter, mail,... ).
>
> SIP makes perfect sense on mobile devices, but
> unfortunately SIP is still far from standardized there.
On the contrary SIP is getting great mileage in 3gpp (www.3gpp.org) and OMA (
http://www.openmobilealliance.org/) and there is also a J2ME JSR for SIP
http://www.jcp.org/en/jsr/detail?id=180 > Implementations are proprietary and differ slightly. I,
> for instance, wish there was a decent open source JME SIP
> implementation...
There are several open source implementations, while you cannot stop people from adding proprietary extensions overall it bodes well for the SIP development as it indicates a vibrant community.