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Is there a way to create a sip network with multiple telephone numbers and just one public telephone? Do I need to have a sip server for this? Can someone give me some ideas? If I need a sip sever how can I create one? I am new to this stuff.

Thanks.

Peter
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elisa
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    What is a SIP server? http://www.3cx.com/PBX/sip-server.html – Peter Mar 15 '11 at 09:24
  • Creating the SIP server itself in C# isn't going to happen, because SIP requires real-time processing for timing and transcoding, I don't think C#, being garbage-collected, can handle that. And unless you require some automation or programming, this is not a question for SO but a question for SuperUser or ServerFault. – Cosmin Prund Mar 15 '11 at 09:30
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    @Cosmin Prund: SIP is a signalling protocol and C# implementations are more than capable of handling its timing requirements. Transcoding and near real-time processing only come into play with RTP and even there the .Net CLR would be fine up to a point. – sipsorcery Mar 15 '11 at 09:41
  • sipwiz can you please light me up in this problem? are there some examples? So a server sip contains a signaling , registrar and rtp? There are 3 servers in one serer? – elisa Mar 15 '11 at 09:44
  • @sipwiz, doesn't connecting the SIP phones to the one "public telephone" require RTP and transcoding? Can a useful implementation of a SIP server be made without RTP? I know you can theoretically get away with no RTP because SIP phones can talk to one another, but then you can get away with no SIP server at all, since SIP allows phones to call one another with no intermediary. – Cosmin Prund Mar 15 '11 at 09:49
  • @elisa: A SIP server can mean a lot of different things. A SIP server will typically fulfil one or more of the following roles: Registrar, Proxy or B2BUA. There are additional server roles such as a redirect server or location server but they are not as common and are generally subsumed into one of the other roles. – sipsorcery Mar 15 '11 at 09:49
  • @Cosmin Prund: Yes for practical purposes connecting to a public telephone will require RTP (not necessarily transcoding though) although Skype is also a popular option but it doesn't use SIP. My previous point was that SIP is not a real-time protocol as such and the .Net CLR is fine for it. If the original request was for a .Net based high volume PSTN gateway then .Net wouldn't be the way to go – sipsorcery Mar 15 '11 at 09:55
  • has anybody tried using the java sipservlet for sip server??? – Vineet Menon Sep 26 '11 at 06:19

2 Answers2

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Creating a SIP server will be rather difficult if you're new to it.

A better way to familiarize yourself with SIP may be to get yourself an old computer and install something like asterisk, or Trixbox community-edition, then work on developing a sip softphone.

The asterisk/trixbox server will then take care of all of your telephone extensions and incoming trunks (I recommend sipgate for incoming trunks, free with 15 simultaneous incoming calls).

There are a lot of open-source sip softphones knocking about, as well as some free .NET sip libraries that you can work with, some of which are discussed here. This will at least help in becoming more familiar with the SIP protocol.

I know this is probably not the answer you were looking for, but I do hope it helps.

Community
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Dave
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If you mean can you have mutliple SIP devices (softphones, ATAs IP Phones etc) all sharing a single PSTN number then the answer is yes. Almost all SIP/VoIP Providers allow you to forward calls from an attached DID (telephone number) to more than one SIP device so your request could be satisfied by a basic account on your friendly neighbourhood VoIP Provider.

Since you included the C# tag you maybe interested in looking at sipsorcery.com which is a project I run and which is based around an open source C# SIP stack.

sipsorcery
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  • are the dll's for the sip server available? – elisa Mar 15 '11 at 09:53
  • Yes sipsorcery.codeplex.com. A word of caution though it's not a project pitched at end users. You ideally need to be both a programmer and already somewhat familiar with SIP to use it. If you just want to get up and running with a SIP Server quickly I'd recommend looking around for a more user friendly alternative. – sipsorcery Mar 15 '11 at 09:57
  • can you give me some links that can help me to create my own sip server inculding the registar, rtp media? – elisa Mar 15 '11 at 10:08
  • @elisa: You really don't want to do that unless you are prepared to spend a year or two working on it (that's no exaggeration). Instead why not try using one of the many already built SIP/RTP/VoIP libraries http://www.pernau.at/kd/voip/bookmarks-sip-stacks.html? – sipsorcery Mar 15 '11 at 10:39
  • thx a lot sipwiz. I would like to ask you if it''s possible the following: A calls B. B forwards the call to C. the final connection is between A and C – elisa Mar 15 '11 at 11:55
  • @elisa: It certainly is. If B talks to A before forwarding it's called an attended transfer. If B doesn't talk and forwards directly it's called a blind transfer. Any decent SIP Provider will support both types of transfers. – sipsorcery Mar 15 '11 at 12:03
  • Thx for answer. is there a demo application? or a link where this application is included? After the registration and invite between B and server , B reiinvites the server using a different uri? – elisa Mar 15 '11 at 12:09
  • could you have an e-mail address?:) Can you please help me a little. I am trying to figure out how this stuff work, what are the sip messages and so on. – elisa Mar 15 '11 at 12:11
  • @elisa: Blind transfer example http://tech-invite.com/Ti-sip-service-04.html. I hang out at forum.sipsorcery.com if you want to ask more detailed SIP questions. – sipsorcery Mar 15 '11 at 12:38
  • what codec should i use for sending a wav over ip? i did use pcm with 16khz 16 bits but the voice is low and it's like a man's voice and not a women's voice like i have. – elisa Mar 15 '11 at 12:49
  • PCM 8kHz 8bits is what the PSTN uses. If you've got problems at 16kHz then I suspect your software is faulty or you are losing a hell of a lot of packets. – sipsorcery Mar 15 '11 at 12:54
  • i am looking over a demo that has a wav extension .pcm16. did you ever heard of this kind of extention? thx:) PS. i have a free sip account ..from the internet. – elisa Mar 15 '11 at 12:58