Character Generator Protocol: Difference between revisions

Revision as of 16:57, 29 March 2016

Revision as of 01:14, 25 March 2017

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{{refimprove|date=October 2015}}

{{IPstack}}

The '''Character Generator Protocol''' ('''CHARGEN''') is a service of the [[Internet Protocol Suite]] defined in RFC{{IETF RFC|864}} in 1983 by [[Jon Postel]]. It is intended for testing, debugging, and measurement purposes. The protocol is rarely used, as its design flaws allow ready misuse.

A host may connect to a server that supports the Character Generator Protocol on either [[Transmission Control Protocol]] (TCP) or [[User Datagram Protocol]] (UDP) [[port number]] 19. Upon opening a TCP connection, the server starts sending arbitrary characters to the connecting host and continues until the host closes the connection. In the UDP implementation of the protocol, the server sends a UDP datagram containing a random number (between 0 and 512) of characters every time it receives a datagram from the connecting host. Any data received by the server is discarded.

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==Sample session==

A typical CHARGEN service session looks like this: The user connects to the host using a [[telnet]] client.

The user receives a stream of [[byte]]s. Although the specific format of the output is not prescribed by RFC{{IETF RFC|864}}, the recommended pattern (and a [[de facto standard]]) is shifted lines of 72 [[ASCII]] characters repeating.

<pre>

$ telnet localhost chargen