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SIP Overview

SIP is an application-layer control protocol that can establish, modify, and terminate multimedia sessions (conferences) such as Internet telephony calls. SIP can also invite participants to already existing sessions, such as multicast conferences. Normally SIP uses UDP and TCP port 5060 and TCP 5061 for SSL communication. SIP protocol is very similar to HTTP, so if you have some knowledge about HTTP, then it is easy to learn SIP. SIP doesn't transfer session data like audio, video. RTP(real time protocol) is used for that, SIP just helps to open RTP streams.

SIP Message Example

INVITE sip:john@domain.com SIP/2.0
From: <sip:doe@domain.com>;tag=2084442460
To: <sip:john@1domain.com>
Via: SIP/2.0/UDP domain.com:5060;branch=z9hG4bK2df7b9194cd51e25
Call-ID: john@domain.com-4524j
CSeq: 1 INVITE
Contact: <sip:doe@domain.com:5060>
Content-Length: 226
Content-Type: application/sdp

<session description data, like RTP description>

SIP Server Types

stateless SIP server doesn't store any transaction info.
statefull SIP server creates and holds SIP commands transaction state.
registrar/location Allows users to register their locations and later to use that info to forward calls to registered contact.
B2BUA SIP server is like statefull + holds active calls state.(This is needed if call billing or full control of call is needed)
presence Provides user availability services, like if user is online,offline, ... .
... There are some more, but not so important ones.

Basic SIP Commands

Ok, some ABC done, there are many documents on the internet, so it is not a good idea to rewrite these there.

If want more advanced information, then see:

SIP Proxy Demo Overview

This SIP proxy example just implements fully functional simple stateless, statefull, b2bua proxy. You can use hardware SIP phones or soft phones to play with this proxy.This is an advanced example, code is well commented, so beginners don't hate me because no more text here. Just read RFC 3216, see information links I noted earlier. After you go through those, if you then look at the code, it is all nicer then.

Some free available softphones are:

Version:
    11.06.2007
        *) Added B2BUA support.
    07.04.2007 
        *) Many bug fixes. 
        *) SIP -> PSTN and PSTN -> SIP gateway support. 
        *) Non-SIP URI gateway support. 

Contact Details

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Generalthanks from PH Pin
mdingalla
21:09 18 Oct '09  
GeneralGeneral comment Pin
mapick
7:36 3 Oct '09  
GeneralSIP Client Pin
binnibinni
3:53 2 Oct '09  
GeneralRe: SIP Client Pin
Ivar Lumi
4:00 2 Oct '09  
GeneralRe: SIP Client Pin
binnibinni
4:04 2 Oct '09  
QuestionUDP to TCP UA Pin
rudacunhasilva
7:34 24 Aug '09  
QuestionSIP TCP Pin
rudacunhasilva
15:48 20 Aug '09  
QuestionSIP_Gateway Pin
rudacunhasilva
11:15 18 Aug '09  
AnswerRe: SIP_Gateway Pin
Ivar Lumi
20:36 18 Aug '09  
GeneralHow to run both SIP Proxy and a client in the same computer? Pin
kaiwnyt
16:36 10 Jul '09  
GeneralRe: How to run both SIP Proxy and a client in the same computer? Pin
Ivar Lumi
21:25 12 Jul '09  
GeneralRe: How to run both SIP Proxy and a client in the same computer? Pin
kaiwnyt
18:32 14 Jul '09  
QuestionSystem.IndexOutOfRangeException: Pin
gokhanuslu
5:18 17 Jun '09  
Generalis there is client Pin
el3ashe2
3:54 11 Jun '09  
GeneralRe: is there is client Pin
Ivar Lumi
7:32 11 Jun '09  
GeneralRe: is there is client Pin
el3ashe2
23:42 13 Jun '09  
GeneralRe: is there is client Pin
Ivar Lumi
20:52 14 Jun '09  
GeneralRe: is there is client Pin
el3ashe2
2:54 15 Jun '09  
GeneralRe: is there is client Pin
Ivar Lumi
3:35 15 Jun '09  
GeneralDoes it work without setting domain Pin
lliaolx_guilin
15:10 10 Jun '09  
GeneralRe: Does it work without setting domain Pin
Ivar Lumi
1:30 11 Jun '09  
GeneralRe: Does it work without setting domain Pin
lliaolx_guilin
8:12 11 Jun '09  
GeneralRe: Does it work without setting domain Pin
Ivar Lumi
8:19 11 Jun '09  
GeneralRe: Does it work without setting domain Pin
lliaolx_guilin
13:53 11 Jun '09  
GeneralRe: Does it work without setting domain Pin
lliaolx_guilin
8:57 11 Jun '09  


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