Discard Protocol

This article is about the Internet protocol named DISCARD. For a definition of the term "discard", see the Wiktionary entry discard.

The Discard Protocol is a service in the Internet Protocol Suite defined in RFC 863. It is intended for testing, debugging, and measurement purposes.

A host may send data to a host that supports the Discard Protocol on either Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) port number 9. The data sent to the server is simply discarded. No response is returned.

Inetd implementation

On most UNIX-like operating systems a discard server is built into the inetd (or xinetd) daemon. The discard service is usually not enabled by default. It may be enabled by adding the following lines to the file /etc/inetd.conf and reloading the configuration:

discard   stream  tcp     nowait  root    internal
discard   dgram   udp     wait    root    internal

The Discard Protocol is the TCP/UDP equivalent of the Unix filesystem node /dev/null. Such a service is guaranteed to receive what is sent to it and can be used for debugging TCP and/or UDP code requiring a guaranteed reception of payload sent.

See also

• List of well-known ports
• Echo Protocol
• Daytime Protocol
• Character Generator Protocol
• Time Protocol

External links

• RFC 348, The Discard process
• RFC 863, The Discard protocol

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