The Discard Protocol is a service in the Internet Protocol Suite

Internet protocol suite

The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...

 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

Transmission Control Protocol

The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

 (TCP) or User Datagram Protocol

User Datagram Protocol

The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

 (UDP) port number 9. The data sent to the server is simply discarded. No response is returned.

Inetd implementation

On most UNIX-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

 operating systems a discard server is built into the inetd

Inetd

inetd is a super-server daemon on many Unix systems that manages Internet services. First appearing in 4.3BSD , it is generally located at /usr/sbin/inetd.-Function:...

 (or xinetd) daemon

Daemon (computer software)

In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...

. 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

/dev/null

In Unix-like operating systems, /dev/null or the null device is a special file that discards all data written to it and provides no data to any process that reads from it ....

. 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
  ECHO protocol
  The Echo Protocol is a service in the Internet Protocol Suite defined in RFC 862. It was originally proposed for testing and measurement of round-trip times in IP networks....
  
  
• Daytime Protocol
• Character Generator Protocol
• Time Protocol
  TIME protocol
  The Time Protocol is a network protocol in the Internet Protocol Suite defined in 1983 in RFC 868. Its purpose is to provide a site-independent, machine readable date and time....