All iFIX network traffic is session-oriented. Transactions between two nodes occur over a session. Before a View client can initiate a request, a session must be established with the SCADA server.
Only one socket is created when using iFIX on a TCP/IP network. However, two logical sessions are maintained. The session initiated by the iClient is used to retrieve data from the SCADA servers. Another session is established from a SCADA server to an iClient to send alarms to the client. In this case, the request portion of the transaction consists of the alarm data and is acknowledged by a response. These two logical sessions are maintained over one physical connection.
To establish a connection, the address of the remote node must be obtained. The method of finding this address, address resolution, is especially important for Wide Area Network (WAN) environments.
