sysread($rh,$buf,4096) || syslog ( "crit", "$prog : $!" );
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You do realize that if sysread returns 0 it is not a critical error and $! will not be set.

       if($buf) {
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You do realize that the string "0" is also false?

           my $client_hostname=unpack('a*', $buf);
           $client_hostname =~ s/\s+$//g;
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If you change the unpack format from 'a*' to 'A*' you won't need the substitution on the next line and it will also remove "\0" characters.