SIP.js API

SIP.js API

sip.js is a simple SIP protocol implementation.

It features:

• SIP Message Parser
• UDP and TCP based transport
• Transactions
• Digest Authentication

Example

Redirecting all SIP requests to backup.somewhere.net

var sip = require('sip');

sip.start({}, function(request) {
  var response = sip.makeResponse(request, 302, 'Moved Temporarily');

  var uri = sip.parseUri(request.uri);
  uri.host = 'backup.somewhere.net'; 
  response.headers.contact = [{uri: uri}];

  sip.send(response);
});

Messages

Parsed SIP messages are javascript objects. Message

INVITE sip:[email protected]:5060 SIP/2.0
Via: SIP/2.0/UDP 127.0.1.1:5060;branch=z9hG4bK-1075-1-0
From: sipp <sip:[email protected]:5060>;tag=1075SIPpTag001
To: sut <sip:[email protected]:5060>
Call-ID: [email protected]
CSeq: 1 INVITE
Contact: sip:[email protected]:5060
Max-Forwards: 70
Subject: Performance Test
Content-Type: application/sdp
Content-Length:   127

v=0
o=user1 53655765 2353687637 IN IP4 127.0.1.1
s=-
c=IN IP4 127.0.1.1
t=0 0
m=audio 6000 RTP/AVP 0
a=rtpmap:0 PCMU/8000

is parsed to following object

{ method: 'INVITE'
, uri: 'sip:[email protected]:5060'
, version: '2.0'
, headers: 
   { via: 
      [ { version: '2.0'
        , protocol: 'UDP'
        , host: '127.0.1.1'
        , port: 5060
        , params: { branch: 'z9hG4bK-1075-1-0' }
        }
      ]
   , from: 
      { name: 'sipp'
      , uri: 'sip:[email protected]:5060'
      , params: { tag: '1075SIPpTag001' }
      }
   , to: 
      { name: 'sut'
      , uri: 'sip:[email protected]:5060'
      , params: {}
      }
   , 'call-id': '[email protected]'
   , cseq: { seq: 1, method: 'INVITE' }
   , contact: 
      [ { name: undefined
        , uri: 'sip:[email protected]:5060'
        , params: {}
        }
      ]
   , 'max-forwards': '70'
   , subject: 'Performance Test'
   , 'content-type': 'application/sdp'
   , 'content-length': 127
   }
, content: 'v=0\r\no=user1 53655765 2353687637 IN IP4 127.0.1.1\r\ns=-\r\nc=IN IP4 127.0.1.1\r\nt=0 0\r\nm=audio 6000 RTP/AVP 0\r\na=rtpmap:0 PCMU/8000'
}    

SIP requests have method and uri properties and responses have status and reason instead.

High Level API

sip.start(options, onRequest)

Starts SIP protocol.

options - an object optionally containing following properties.

• port - port to be used by trasport. 5060 by default.
• address - interface address to be listen on. By default sip.js listens on all interfaces.
• udp - enables UDP transport. Enabled by default.
• tcp - enables TCP transport. Enabled by default.

onRequest - callback to be called on new request arrival. It is expected to be a function of two arguments function (request, remote) {}. First argument request is a received request. Second argument remote is an object containing protocol, address and port of a remote socket used to send the request. For example { protocol: 'TCP', address: '192.168.135.11', port: 50231 }

sip.stop

Stops SIP protocol.

sip.send(message[, callback])

Sends SIP message transactionally.

If message is an non-'ACK' request then client transaction is created. Non-'ACK' requests are passed directy to transport layer.

If message is a response then server transaction is looked up and passed the message. There is no special handling of success responses to 'INVITE' requests. It is not necessary because in sip.js 'INVITE' server transactions are not destroyed on 2xx responses but kept around for another 32 seconds (as per RFC 6026). Applications still need to resend success 'INVITE' responses.

Helper Functions

sip.makeResponse(request, status[, reason])

returns SIP response object for request with status and reason fields set.

sip.parseUri(uri)

parses SIP uri.

sip.stringifyUri(uri)

stringifies SIP uri.

sip.parse(message)

parses SIP message.

sip.stringify(message)

stringfies SIP message.

sip.copyMessage(message[, deep])

copies SIP message. If parameter deep is false or omitted it copies only method, uri, status, reason, headers, content fields of root object and headers.via array. If deep is true it performs full recursive copy of message object.

Digest Authentication

sip.js implements digest authentication as described in RFC 2617. Module can be accessed by calling require('sip/digest');

Server-side API

digest.challenge(session, response)

inserts digest challenge ('WWW-Authethicate' or 'Proxy-Authenticate' headers) into response and returns it. session parameter is a javascript object containing at least realm property. On return it will contain session parameters (nonce, nonce-count etc) and should be passed to subsequent authenticateRequest calls. It is a plain object containing only numbers and strings and can be 'jsoned' and saved to database if required.

digest.authenticateRequest(session, request[, credentials])

returns true if request is signed using supplied challenge and credentials. credentials required only on first call to generate ha1 value which is cached in session object. credentials is an object containing following properties:

• user - user's account name
• realm - protection realm name. optinal, should match realm passed in corresponding challenge call.
• password - user's password. optional if hash property is present.
• hash - hash of user's name, password and protection realm. Optional if password is present. Can be obtained by calling digest.calculateUserRealmPasswordHash and used if you don't want to store passwords as clear text.

digest.signResponse(session, response)

inserts 'Authentication-Info' header into response. Used for mutual client-server authentication.

Client-side API

digest.signRequest(session, request[, response, credentials])

inserts 'Authorization' or 'Proxy-Authorization' headers into request and returns it. To initialize the session after server challenge reception, supply response (must be 401 or 407 response containing server challenge) and credentials. credentials parameter described in digest.authenticateRequest description.

digest.authenticateResponse(session, response)

checks server signature in 'Authentication-Info' parameter. Returns true if signature is valid, false if invalid and undefined if no 'Authentication-Info' header present or it lacks rspauth parameter. If server supplied nextnonce parameter reinitializes session.

Low level functions

digest.calculateDigest(arguments)

calculates digest as described in RFC 2617. arguments is an object with following properties

• ha1
• nonce
• nc
• cnonce
• qop
• method
• uri
• entity

digest.calculateHA1(arguments)

calculates H(A1) value as described if RFC 2617. arguments is an object with followin properties

• userhash - hash of user's name, realm and password. Optional if user, realm and password properties are present
• user - user's name. Optional if userhash is present.
• realm - realm name. Optional if userhash is present.
• password - user's password in realm. Optional if userhash is present.
• algorithm - authentication algorithm. Optional, by default used value md5.
• nonce - server's nonce parameter. Optional if algorithm is not equal to md5-sess
• cnonce - client's nonce. Optional if algorithm is not equal to md5-sess

digest.calculateUserRealmPasswordHash(user, realm, password)

calculates hash of 'user:realm:password'

Proxy Module

sip.js includes proxy module to simplify proxy server development. It can be accessed via require('sip/proxy'); Usage example:

var sip = require('sip');
var proxy = require('sip/proxy');
var db = require('userdb');

proxy.start({}, function(rq) {
  var user = sip.parseUri(rq.uri).user;

  if(user) {
    rq.uri = db.getContact(user);

    proxy.send(rq);
  }
  else
    proxy.send(sip.makeResponse(rq, 404, 'Not Found')); 
});

proxy.start(options, onRequest)

Starts proxy and SIP stack. Parameters are analogous to sip.start

proxy.stop

stops proxy core and sip stack.

proxy.send(msg[, callback])

Use this function to respond to or to make new requests in context of incoming requests. Proxy core will automatically handle cancelling of incoming request and issue CANCEL requests for outstanding requests on your behalf. Outgoing requests are bound to context through their top via header. If you are sending a request and omit callback parameter, default calback will be used:

function defaultProxyCallback(rs) {
  // stripping top Via
  rs.headers.via.shift();

  // sending response to original incoming request
  proxy.send(rs);
}