How a Session is Initialized

Once a TCP connection has been established, a client attempts to initialize a communications session by sending an OPEN_REQ message, defined in OPEN_REQ, to the server. The server responds with an OPEN_CONF message, defined in OPEN_REQ, to confirm the successful establishment of a session. Figure 1 depicts the message flow.

If the server rejects an OPEN_REQ message, the client must reset the TCP connection. The status code received in the rejection (see Error (E) Status Codes) indicates the message data that must be corrected before retrying the attempt to establish a session. It is a good practice to wait for at least 10 seconds before retrying the OPEN_REQ message.

The OPEN_REQ message contains protocol version information. The minimum version number supported by Unified CCX is 10. In general, Unified CCX maintains backward compatibility in new product releases.