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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.

Postel [Page 1]