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The Echo service is an Internet protocol defined in RFC 862. It was originally proposed for testing and measurement of round-trip times in IP networks. Now, testing and measurement is more commonly done with the ICMP protocol using the applications ping and traceroute.
A host may connect to a server that supports the Echo protocol on either TCP or UDP port 7. The server then sends back any data it receives, with no modification by the Echo server.
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Inetd implementation of Echo
On Linux, FreeBSD, and other UNIX-like operating systems an Echo server is built into the inetd daemon. 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
Examples of use
- As a generic network service which is guaranteed to read, and additionally write back, what is sent to it. Such a service is useful for debugging TCP and UDP based network code (such as event-loops) without disrupting the current operation of existing services.
