Rlogin

In computing, rlogin is a Unix program that allows users to log in on another host using a network. rlogin uses TCP port 513. It was first distributed as part of the 4.2BSD release. rlogin is also the name of the application layer protocol used by the software, also the protocol is part of the TCP/IP protocol suite.
The rlogin homepage is located at http://rlogin.sourceforge.net.
rlogin has several serious security problems, the most important are:
Due to its serious problems, rlogin was rarely used across untrusted networks (like the public internet), and rlogin distributions are no longer included by default with many Unix and Linux distributions. Many networks which were depending on rlogin and telnet have replaced it with SSH and the "rlogin secured equivalent" slogin.