This RFCspecifies a standard for the ARPA Internet community. Hosts on the ARPA Internet that choose to implement a Character Generator Protocol are eXPected to adopt and implement this standard.
A useful debugging and measurement tool is a character generator service. A character generator service simply sends data without regard to the input.
TCP Based Character Generator Service
One character generator service is defined as a connection based application on TCP. A server listens for TCP connections on TCP port 19. Once a connection is established a stream of data is sent out the connection (and any data received is thrown away). This continues until the calling user terminates the connection.
It is fairly likely that users of this service will abruptly decide that they have had enough and abort the TCP connection, instead of carefully closing it. The service should be prepared for either the carfull close or the rude abort.
The data flow over the connection is limited by the normal TCP flow control mechanisms, so there is no concern about the service sending data faster than the user can process it.
UDP Based Character Generator Service
Another character generator service is defined as a datagram based application on UDP. A server listens for UDP datagrams on UDP port 19. When a datagram is received, an answering datagram is sent containing a random number (between 0 and 512) of characters (the data in the received datagram is ignored).
There is no history or state information associated with the UDP version of this service, so there is no continuity of data from one answering datagram to another.
The service only send one datagram in response to each received datagram, so there is no concern about the service sending data faster than the user can process it.
RFC864 May 1983 Character Generator Protocol
Data Syntax
The data may be anything. It is recommended that a recognizable pattern be used in tha data.
One popular pattern is 72 chraracter lines of the ASCII printing characters. There are 95 printing characters in the ASCII character set. Sort the characters into an ordered sequence and number the characters from 0 through 94. Think of the sequence as a ring so that character number 0 follows character number 94. On the first line (line 0) put the characters numbered 0 through 71. On the next line (line 1) put the characters numbered 1 through 72. And so on. On line N, put characters (0+N mod 95) through (71+N mod 95). End each line with carriage return and line feed.
