====== answer ======
**C → S → C {type:'answer', sdp:...}**

answer – SDP answering a call.

SDP answer sent by client to server as a response to received call [[ixnx:wrtc:rtcgate:offer|offer]]. Server forwards answer to calling client.

arguments:
  * sdp - [[https://en.wikipedia.org/wiki/Session_Description_Protocol|SDP]] containing streaming media communications parameters
  * from - address of this client
  * to - address of remote client

optional argument:
  * from_dn - display name of this client
  * error - an error has occurred:
    * 281: [[ixnx:wrtc:rtcgate:newsdp|newsdp]] not supported by remote browser, returned SDP is only a dummy one. //(The sent SDP in [[ixnx:wrtc:rtcgate:newsdp|newsdp]] message was ignored, this answer SDP is the same as sent before. Depending on browser the transmission may now become hung or one-way.)//

optional argument for group calls:
  * gid - group call ID

optional arguments when transferring a call:
  * transferred_by - address of client transferring call
  * replacing - address of client old call was to