doc/sp.plantuml

   1      ┌─────────┐                       ┌─────────┐
   2      │Initiator│                       │Responder│
   3      └────┬────┘                       └────┬────┘
   4           │                                 │
   5           │         ╔═════════════╗         │
   6 ══════════╪═════════╣ preparation ╠═════════╪══════════
   7           │         ╚═════════════╝         │
   8           │                                 │
   9           │              [s]                │
  10           │<────────────────────────────────│
  11           │                                 │
  12           │                                 │
  13           │         ╔═════════════╗         │
  14 ══════════╪═════════╣ interactive ╠═════════╪══════════
  15           │         ╚═════════════╝         │
  16           │                                 │
  17           │[e, es, s, ss], INFO..., HALT... │
  18           │────────────────────────────────>│
  19           │                                 │
  20           │ [e, ee, se], INFO..., HALT...   │
  21           │<────────────────────────────────│
  22           │                                 │
  23           │   INFO..., FREQ..., DONE...     │
  24           │────────────────────────────────>│
  25           │                                 │
  26           │   INFO..., FREQ..., DONE...     │
  27           │<────────────────────────────────│
  28           │                                 │
  29           │FILE..., INFO..., DONE..., PING  │
  30           │────────────────────────────────>│
  31           │                                 │
  32           │FILE..., INFO..., DONE..., PING  │
  33           │<────────────────────────────────│
  34           │                                 │