rexec has the same kind of functionality that rsh has : you can execute shell commands on a remote computer.
Contents
The main difference is that rexecd authenticates by reading the username and password (unencrypted) from the socket.
Limitations
Same as rsh: sends unencrypted information over the network, including passwords.
Port number
rexec uses well-known port TCP 512.
References
Remote Process Execution Wikipedia(Text) CC BY-SA