Client Server | | +------>| Code: 0.03 (PUT) | PUT | Token: 0x41 | | Uri-Path: lock | | Payload: 0 (Unlock) | | |<------+ Code: 4.01 (Unauthorized) | 4.01 | Token: 0x41 | | Echo: 0x05 (e0 = 5, number of total lock | | operations performed) | | | ... | No alterations happen to the lock state, e1 has the | | same value e1 = 5. | | +------>| Code: 0.03 (PUT) | PUT | Token: 0x42 | | Uri-Path: lock | | Echo: 0x05 | | Payload: 0 (Unlock) | | | | Compare e1 = e0 => permitted. | | |<------+ Code: 2.04 (Changed) | 2.04 | Token: 0x42 | | Echo: 0x06 (e2 = 6, to allow later locking | | without more round trips) | |