Failure and End Causes

SIP.js provides a set of causes in order to make the user aware of why the request or session ended. These causes are defined in the SIP.C.causes namespace, which can be used for comparisons.

// Create a user agent named bob, connect, and register to receive invitations.
var bob = new SIP.UA({
  uri: 'bob@example.com',
  register: true

var session =  bob.invite('alice@example.com');
session.on('failed', function (request) {
  var cause = request.cause; //sometimes this is request.reason_phrase
  if (cause === SIP.C.causes.REJECTED) {
    bob.message('alice@example.com', 'Please, call me later!');

Common Causes

Constant Value Description
INVALID_TARGET ‘Invalid target’ The specified target can not be parsed as a valid SIP.URI.
CONNECTION_ERROR ‘Connection Error’ WebSocket connection error occurred.
REQUEST_TIMEOUT ‘Request Timeout’ The timeout expired for the client transaction before a response was received.
SIP_FAILURE_CODE ‘SIP Failure Code’ A negative SIP response was received which is not part of any of the groups defined in the table below.

SIP Error Causes

Some SIP response status codes are grouped into the following causes:

Constant Value SIP Status Codes
BUSY ‘Busy’ 486,600
REJECTED ‘Rejected’ 403,603
REDIRECTED ‘Redirected’ 300,301,302,305,380
UNAVAILABLE ‘Unavailable’ 408,410,430,480
NOT_FOUND ‘Not Found’ 404,604
ADDRESS_INCOMPLETE ‘Address Incomplete’ 484
INCOMPATIBLE_SDP ‘Incompatible SDP’ 488,606
AUTHENTICATION_ERROR ‘Authentication Error’ 401,407

Session Causes

The following causes apply to audio/video sessions:

Constant Value Description
BYE ‘Terminated’ Session terminated normally by local or remote peer.
CANCELED ‘Canceled’ Session canceled by local or remote peer.
NO_ANSWER ‘No Answer’ Incoming call was not answered in the time given in the configuration no_answer_timeout parameter.
EXPIRES ‘Expires’ Incoming call contains an Expires header and the local user did not answer within the time given in the header.
NO_ACK ‘No ACK’ An incoming INVITE was replied to with a 2XX status code, but no ACK was received.
NO_PRACK ‘No PRACK’ An incoming iNVITE was replied to with a reliable provisional response, but no PRACK was received.
USER_DENIED_MEDIA_ACCESS ‘User Denied Media Access’ Local user denied media access when prompted for audio/video devices.
WEBRTC_NOT_SUPPORTED ‘WebRTC not supported’ The browser or device does not support the WebRTC specification.
RTP_TIMEOUT ‘RTP Timeout’ There was an error involving the PeerConnection associated with the call.
BAD_MEDIA_DESCRIPTION ‘Bad Media Description’ Received SDP is wrong.
DIALOG_ERROR ‘Dialog Error’ An in-dialog request received a 408 or 481 SIP error.