Implement Control component with TCP/IP

State Machines

TCPClient

States:

IDLE, DISCONNECTED, CONNECTING, CONNECTED

Transitions:

DISCONNECTED -> CONNECTING -> CONNECTED
CONNECTING | CONNECTED -> DISCONNECTED (transient failures) CONNECTING | CONNECTED -> IDLE (connecting failed/connection lost, disconnect on request)

Properties: LastSeen (time since last successful message received or written to)

Control Component

States (like modules):

OFFLINE, INITIALIZING, ONLINE, SHUTDOWN, FAILED

Workflow

Control OFFLINE

if Autostart enabled and TCPClient DISCONNECTED start connecting (TCPClient -> CONNECTING, Control -> INITIALIZING)
if TCPClient IDLE or autostart disabled on user intervention Control -> INITIALIZING, start connecting, TCPClient -> CONNECTING

Control INITIALIZING

if Autostart enabled and TCPClient DISCONNECTED start connecting (TCPClient -> CONNECTING, Control -> INITIALIZING)
if TCPClient IDLE Control -> FAILED
if TCPClient CONNECTED enable modules with Autostart (send ENABLE) and Control -> ONLINE

Control ONLINE

if TCPClient IDLE Control -> FAILED
if user requests disconnect send DISABLE to all enabled modules, Control -> SHUTDOWN
check if some messages are pending, update module states (ENABLED, DISABLED, FAILED)
if TCPClient CONNECTED and LastSeen > defined send KEEPALIVE message

Control SHUTDOWN

check if messages are pending, update module states accordingly
if no more modules in ENABLED state Control -> OFFLINE, disconnect, TCPClient -> IDLE

Control FAILED

on user intervention Control -> INITIALIZING, start connecting, TCPClient -> CONNECTING

When stopping ev3dev-mapping-ui:

if ONLINE send DISABLE_ALL message, disconnect, Control -> SHUTDOWN, TCPClient -> IDLE
if INITIALIZING,canel connection,, Control -> SHUTDOWN, TCPClient -> IDLE

Notes

whenever send fails TCPClient -> IDLE
see bmegli/ev3dev-mapping/issues/18 to understand how replay infrastructure affects above

bmegli / ev3dev-mapping-ui