2.2. Communication

The following sections describe the communication behavior of the Eclipse SCADA system.

Eclipse SCADA has two different behaviors for connections to servers. One manual mode and one automatic mode. The decision is done by the application which mode to use. It cannot be configured in the connection string itself.

The easier version is the manual mode. Establishing the connection is manually triggered (e.g. by a user) and manually closed. If the connections breaks, it simply stays closed. This mode is, for example, used in the ESAC application. Connections are opened and closed on user request. If the connection breaks, an error message displayed to the user and the connection stays closed until the user re-opens.

In automatic mode the application simply decides weather the connection should stay open or stay closed. Eclipse SCADA manages then the connection state and will trigger connect and disconnect calls automatically. In most cases the application simply requests the connection to be open. This mode is primarily used by the master server or the normal end user client.

When the connection is requested to be opened, the appropriate call is made to the connection itself. If the connection break a re-connect will be triggered immediately. The time of this requested will be noted and the next action (connect or disconnect) will be delayed by the quiet period. The default quiet period is 10 seconds, but can be changed using the system property org.eclipse.scada.default.reconnect.delay which holds the time in milliseconds. So if the connection breaks and the first reconnect fails, the next reconnect will not be tried until the quiet period is over. After that the next connection attempt will be made.

The protocols Eclipse SCADA provides are normally based on plain TCP client/server protocols. Each driver and application provides services on different TCP ports. The follow map provides a list of well known ports in the Eclipse SCADA system.

For an update to list, see also the Eclipse SCADA Wiki page at https://wiki.eclipse.org/EclipseSCADA/Documentation/StandardPorts .