telnet-probe — lightweight telnet-like port probe
$PCP_BINADM_DIR/telnet-probe [-c] [-v] host port
telnet-probe allows the pmdashping(1) daemons to establish connections to arbitrary local and remote service-providing daemons so that response time and service availability information can be obtained.
The required host and port number arguments have the same meaning as their telnet(1) equivalents.
The -c option causes telnet-probe to perform a connect(2) only. This skips the read(2) and write(2) exercise that would otherwise be done after connecting (see below).
The -v option causes telnet-probe to be verbose while operating.
Once the telnet connection has been established, telnet-probe reads from stdin until end-of-file, and writes all the input data to the telnet connection. Next, telnet-probe will read from the telnet connection until end-of-file, discarding whatever data it receives. Then telnet-probe exits.
To operate successfully, the input passed via telnet-probe to the remote service must be sufficient to cause the remote service to close the connection when the last line of input has been processed, e.g. ending with “quit” when probing SMTP on port 25.
By default telnet-probe will not produce any output, unless there is an error in which case a diagnostic message can be displayed (in verbose mode only) and the exit status will be non-zero indicating a failure.
Environment variables with the prefix PCP_ are used to parameterize the file and directory names used by PCP. On each installation, the file /etc/pcp.conf contains the local values for these variables. The $PCP_CONF variable may be used to specify an alternative configuration file, as described in pcp.conf(5).
If telnet-probe succeeds, then 0 will be returned. If the attempt to establish a connection fails or is terminated, then a non-zero exit status is returned.
PCPintro(1), pmdashping(1), pmie(1), telnet(1), connect(2), read(2) and write(2).