Clients, servers, and the secure file
When a BMC Server Automation application on a client attempts to connect to an RSCD daemon on a server, the application first checks the secure file for a client to see how the connection should be established. If an entry for the target server exists in the secure file, the application checks the secure file to see if and how the connection should be redirected and whether data should be encoded, encrypted, or sent as clear text. If an entry for the remote host is not found, the application searches for an entry called default to determine how the connection to the remote host should be made. (For more on configuring entries in the secure file, see Configuring the secure file.) If the secure file does not include an entry for the remote host or a default entry, the attempt to establish a connection is aborted.
TCP is a bi-directional virtual circuit protocol. As such, when a client establishes a connection to an RSCD daemon on a server, that connection is used to both send and receive data.
To determine where to listen for connection requests, the RSCD daemon consults the secure file on the server. It looks for an entry for a host named rscd. If an entry is not found, the daemon listens by default to port 4750 (or as otherwise defined in the Internet services databases). If an rscd entry is found, the software treats it as a special entry used by the RSCD daemon. The rscd entry can specify which port and address to listen to for connection requests and it can specify default communication parameters. (For more information about configuring the rscd entry, see Configuring the secure file.) The RSCD daemon can listen on a specified port on all available NICs or a particular NIC (specified using the host= field, as described in Options for secure file). The RSCD daemon cannot listen to a port on a list of specified NICs. In other words, it can only listen on one NIC or all NICs.
When a client establishes a connection, the RSCD daemon again refers to the secure file to determine what data encoding/encryption it should expect from the client host. The RSCD first checks for an entry for the connecting host. If such an entry exists, the agent uses the connection parameters defined in that entry. If no entry for the connecting host is found, the daemon uses the default values from the rscd entry.