offer

C → S → C {type:'offer', sdp:…}

offer – SDP offer starting a call.

Client wanting to start a call sends an SDP offer to server, server forwards it to requested client. That client should send an answer message to accept the call.

arguments:

• sdp - SDP containing streaming media communications parameters
• from - address of caller
• to - address to call

optional argument:

• from_dn - display name of caller

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