Permanent vs. transient connections

[4ZM]

Implement two connection modes. One permanent (connect - sync - wait -sync - ... ) and one transient (connect - sync - disconnect).

Update the protocol with new commands for the permanent connection type: TURN, WAIT, ALIVE CHECK

Update the protocol document.

Implement in a way that:
A) Re-uses the same code for a single direction sync in all cases
B) Is oblivious of the underlying data transfer mechanism (tcp/ip, bluetooth, etc.)
C) Introduces a minimum amount of state in the client server connection.
D) Is resilient to denial of service by resource (connection & thread) exhaustion.