sequenceDiagram
  participant A as Alice
  participant AC as Alice Chat
  participant AA as Alice Agent
  participant XFTP as Alice's XFTP relay(s)
  participant SMP as Bob's SMP relay
  participant BA as Bob Agent
  participant BC as Bob Chat
  participant B as Bob
  
  A ->> AC: APISendMessage
  AC ->> AA: sendMessage(x.msg.new) /<br>CIFSSndStored
  AA ->> SMP: SEND<x.msg.new>
  SMP ->> BA: MSG<x.msg.new>
  BA ->> BC: MSG<x.msg.new>
  BC ->> B: CRNewChatItem<br>(file not ready)
  B ->> BC: ReceiveFile
  BC ->> B: error: no file description
  AC ->> AA: sendFile
  AC ->> A: CRSndFileStart
  AA ->> XFTP: chunk (FNEW, FPUT)
  AA ->> AC: SFPROG /<br>CIFSSndTransfer
  AC ->> A: CRSndFileProgress (new)
  AA ->> XFTP: chunks
  AA ->> AC: SFDONE sd rds
  AC ->> AA: sendMessage(x.msg.file.descr) /<br>FSComplete / CIFSSndComplete
  AC ->> A: CRSndFileComplete (?)
  AA ->> SMP: SEND<x.msg.file.descr>
  SMP ->> BA: MSG<x.msg.file.descr>
  BA ->> BC: MSG<x.msg.file.descr>
  BC ->> B: CRChatItemUpdated<br>(file is ready)
  BC ->> B: CRFileReady (TBC)
  B ->> BC: ReceiveFile
  BC ->> BA: getFile
  BC ->> B: CRRcvFileStart
  XFTP ->> BA: chunk (FGET / FRFile)
  BA ->> BC: RFPROG
  BC ->> B: CRRcvFileProgress (new)
  XFTP ->> BA: chunks
  BA ->> BC: RFDONE
  BC ->> B: CRNewChatItem<br>(file received)
  BC ->> B: CRRcvFileComplete