11-21-2002
Re: /etc/services is not used to configure ports.
Quote:
Originally posted by Neo
/etc/services is not (generally) used to change ports.
Well, I must say that that with the versions of unix that I am familiar with, /etc/services does indeed control which ports a program will use.
To verify that this is still true I signed in to a Solaris 8 and a HP-UX 11 system. I did a "telnet localhost" and verified that I got a telnet session. Then I changed /etc/services so that the telnet entry said 21/tcp rather than 23/tcp. Then I repeated the "telnet localhost" test. In both cases I was now talking to a ftp server.
Yes, the telnet program does offer the user a way to override the default port on the command line. But even there, an /etc/services search is performed if the port is non-numeric. That's why "telnet localhost 25" and "telnet localhost smtp" both work.
Doesn't your unix system behave the same way?
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LEARN ABOUT CENTOS
telnet-probe
TELNET-PROBE(1) General Commands Manual TELNET-PROBE(1)
NAME
telnet-probe - lightweight telnet-like port probe
SYNOPSIS
$PCP_BINADM_DIR/telnet-probe [-c] [-v] host port
DESCRIPTION
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 tel-
net 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 ver-
bose mode only) and the exit status will be non-zero indicating a failure.
PCP ENVIRONMENT
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 configura-
tion file, as described in pcp.conf(5).
DIAGNOSTICS
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.
SEE ALSO
PCPintro(1), pmdashping(1), pmie(1), telnet(1), connect(2), read(2) and write(2).
Performance Co-Pilot PCP TELNET-PROBE(1)