Reconnection and exception

API reconnection

The Tango API automatically manages re-connection between client and server in case of communication error during a network access between a client and a server. The transparency reconnection mode allows a user to be (or not be) informed that automatic reconnection took place. If the transparency reconnection mode is not set, when a communication error occurs, an exception is returned to the caller and the connection is internally marked as bad. On the next try to contact the device, the API will try to re-build the network connection. If the transparency reconnection mode is set (the default case), the API will try to re-build the network connection has soon as the communication error occurs and the caller is not informed. Several cases are possible. They are summarized in the following table:

Case	Server state	Call nb	Exception (transparency false)	Exception (transparency true)
Server killed and re-started	Server killed before call n	n	CommunicationFailed	ConnectionFailed
	Down	n + 1	ConnectionFailed (2 levels)	idem
	Down	n + 2	idem	idem
	Running	n + x	No exception	No exception
Server died and re-started	Server died before call n	n	CommunicationFailed	ConnectionFailed
	Died	n + 1	ConnectionFailed (3 levels)	idem
	Died	n + 2	idem	idem
	Running	n + x	No exception	No exception
Server killed and re-started	Server killed and re-started before call n	n	CommunicationFailed	No exception
	Running	n + x	No exception	No exception
Server died and re-started	Server died and re-started before call n	n	CommunicationFailed	No exception
	Running	n + x	No exception	No exception

Please note that the timeout case is managed differently because it will not enter the re-connection system. The transparency reconnection mode is set by default to true starting with Tango version 5.5.