On
UNIX-like operating systems an echo server is built into the
inetd family of
daemons. The echo service is usually not enabled by default. It may be enabled by adding the following lines to the file and telling inetd to reload its configuration: echo stream tcp nowait root internal echo dgram udp wait root internal On various routers, this TCP or UDP port 7 for the Echo Protocol for relaying
ICMP datagrams (or port 9 for the
Discard Protocol) is also configured by default as a proxy to relay
Wake-on-LAN (WOL) magic packets from the Internet to hosts on the local network in order to wake them up remotely (these hosts must also have their network adapter configured to accept WOL datagrams and the router must have this proxy setting enabled, and possibly also a configuration of forwarding rules in its embedded
firewall to open these ports on the Internet side). ==See also==