RFC 862 INTERNET STANDARD TESTING · APPLICATION

Echo Protocol

A simple TCP or UDP service that sends received data back to its sender.

RFC EDITOR

Postel, J., "Echo Protocol", STD 20, RFC 862, DOI 10.17487/RFC0862, May 1983, <https://www.rfc-editor.org/info/rfc862>.

BIBTEX

@misc{rfc862,
  series = {Request for Comments},
  number = 862,
  howpublished = {RFC 862},
  publisher = {RFC Editor},
  doi = {10.17487/RFC0862},
  url = {https://www.rfc-editor.org/info/rfc862},
  author = {J. Postel},
  title = {{Echo Protocol}},
  pagetotal = 1,
  year = 1983,
  month = may,
}

PUBLISHED: May 1983
AUTHORS: J. Postel
STREAM: Legacy
TCP PORT: 7
UDP PORT: 7
DOI: 10.17487/RFC0862

RFC text

Original text · RFC Editor View on rfc-editor.org ↗

Network Working Group                                          J. Postel
Request for Comments: 862                                            ISI
                                                                May 1983



                             Echo Protocol




This RFC specifies a standard for the ARPA Internet community.  Hosts on
the ARPA Internet that choose to implement an Echo Protocol are expected
to adopt and implement this standard.

A very useful debugging and measurement tool is an echo service.  An
echo service simply sends back to the originating source any data it
receives.

TCP Based Echo Service

   One echo service is defined as a connection based application on TCP.
   A server listens for TCP connections on TCP port 7.  Once a
   connection is established any data received is sent back.  This
   continues until the calling user terminates the connection.

UDP Based Echo Service

   Another echo service is defined as a datagram based application on
   UDP.  A server listens for UDP datagrams on UDP port 7.  When a
   datagram is received, the data from it is sent back in an answering
   datagram.

ISO Plain Language

On this page

PROBLEMA simple service is useful for debugging and measuring whether a network path can carry data.

MECHANISMAn Echo server listens on port 7 and returns the data it receives, using a TCP stream or an answering UDP datagram.

WHAT IT DOESThe RFC defines the behavior for hosts that choose to implement the Echo Protocol. The same data is returned without interpretation.

§1A Basic Test Service

An echo service sends back any data it receives. The RFC describes it as a useful tool for debugging and measurement.

Hosts that choose to implement the protocol are expected to follow the behavior described in this memo.

The service returns the data sent to it. This makes it a simple way to check a network connection.

§2Echo over TCP and UDP

For TCP, a server listens on TCP port 7. After a connection is established, it sends back any data received and continues until the user ends the connection.

For UDP, a server listens on UDP port 7. For each datagram it receives, it sends the same data back in an answering datagram.

With TCP, the server returns data over the open connection until the user ends it. With UDP, each message sent to the server gets a matching message back.

§3The Echoed Data

The service returns the received data to its source. The RFC does not describe additional processing or require a particular message format.

The server sends back the data it received, without changing the service into a more complex exchange.