telnet 0 = telnet `hostname`

By OK -
telnet 0 = telnet `hostname`

When an application uses 0.0.0.0 (the same as 0) as the address in a
connect() call, the OS looks for one of the system's actual addresses and
replaces it with that.  So "telnet 0" is essentially the same as "telnet
`hostname`" if the host only has one address.
telnet 127.0.0.1 will connect to the loopback interface rather than the
systems's network interface.

The differences are very slight.  For instance, if you do "telnet
127.0.0.1" and login, "who" will show that you logged in from localhost.
But if you do "telnet 0" or "telnet `hostname`" you will be shown as having
logged in from your hostname.

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