The Echo Protocol is a service in the

Internet Protocol Suite The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...

defined in RFC 862. It was originally proposed for testing and measurement of

round-trip time In telecommunications, round-trip delay (RTD) or round-trip time (RTT) is the amount of time it takes for a signal to be sent ''plus'' the amount of time it takes for acknowledgement of that signal having been received. This time delay includes p ...

s in IP networks. A host may connect to a server that supports the Echo Protocol using the

Transmission Control Protocol The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly ...

(TCP) or the

User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) network. ...

(UDP) on the well-known

port number In computer networking, a port is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an operating system, a port is a logical construct that identifies a specific ...

7. The server sends back an identical copy of the data it received.

Inetd implementation

UNIX-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating systems an echo server is built into the

inetd inetd (internet service daemon) is a super-server daemon on many Unix systems that provides Internet services. For each configured service, it listens for requests from connecting clients. Requests are served by spawning a process which runs the ...

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 The Discard Protocol is a service in the Internet Protocol Suite defined in RFC 863. It was designed for testing, debugging, measurement, and host-management purposes. A host may send data to a host that supports the Discard Protocol on either ...

) 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 Firewall may refer to: * Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts * Firewall (construction), a barrier inside a building, designed to limit the spre ...

to open these ports on the Internet side).

References

{{reflist

External links

RFC 347 Echo ProcessRFC 862 Echo Protocol
Application layer protocols

Inetd implementation

See also

References

External links