Each service is defined by its operational characteristics, generally different from one service to another.

The way to determine if a particular service is in operational state varies based on service type.

NDE_PORT_CHECK rules can be used to determine basic TCP port connectivity (for example, a HTTP server would normally be listening on port 80).

More thorough checking is by using a telnet program to connect to the port 80 and issue “GET /” command. This should return a default web document. If the returned text contains HTML token, the test is considered successful.

Similarly, other network services can be tested using similar technique. For a demonstration of this approach, see SCP_LINUX_HTTP_OPERATIONAL.

Going beyond access/operability checks is Argent Sentry, providing FTP_EXISTS_PUB_FILES, EML_SEND_TEST_ONLY, RSP_OFFLINE_SERVER, RLB_HOME_PAGE and others to check accessibility and correct operation of most common network services.

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