Echo Protocol


The Echo Protocol is a service in the Internet Protocol Suite defined in RFC 862. It was originally proposed for testing and measurement of round-trip times in IP networks.
A host may connect to a server that supports the Echo Protocol using the Transmission Control Protocol or the User Datagram Protocol on the well-known port number 7. The server sends back an identical copy of the data it received.

Inetd implementation

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 /etc/inetd.conf 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 is also configured by default as a proxy to relay Wake-on-LAN magic packets from the Internet to hosts on the local network in order to wake them up remotely.