Björn Felten -> All skrev 2014-11-07 00:57:

FTS-0004 Echomail Specification

WHAT IS ECHOMAIL?

Echomail is a technique to permit several nodes on the Fidonet
network to share messages. All systems sharing a given conference see
any messages entered into the Echo by any of the participating
systems.

HOW IT WORKS

Echomail is functionally compatible with Netmail. In general, the
process is:

1. A message is entered into a designated area on a FidoNet
compatible system.

2. This message is "Exported" along with some control information
to each system "linked" to the Echo through the originating
system.

3. Each of the receiving systems "Import" the message into the
proper Echomail area.

4. The receiving systems then "Export" these messages, along with additional control information, to each of their conference
links.

5. Return to step 3.

Following the steps literally would mean messages would never stop
being exported and transmitted to other systems. The information
contained in the 'control information' section is used to prevent transmitting the same message more than once to a single system.

CONTROL INFORMATION

There are five pieces of control information associated with an
Echomail message. Some are optional, some are not. The following
control fields determine how Echomail is handled:

1. Area line

This is the first line of an Echomail message. Its actual appearance
is:

AREA:ECHO

Where ECHO the name of the conference. This line is added when an
Echo is being "Exported" to another system. It is based upon
information found in a configuration file for the designated message
area. This field is REQUIRED by the receiving system to "Import" a
message into the correct Echomail area.

2. Tear Line

This line is near the end of a message and consists of three dashes
(---) followed by an optional program specifier. This is used to show
the first program used to add Echomail compatible control information
to the message. The tear line generated looks like:

--- <a small product-specific banner>

This line is optional.

3. Origin line

This line appears near the bottom of a message and gives a small
amount of information about the system where it originated. It looks
like:

* Origin: The EchoMail BBS (1:132/101)

The " * Origin: " part of the line is a constant field. This is
followed by the name of the system as taken from a config file. The complete network address (1:132/101 in this case) is added by the
program inserting the line. The field is generated at the same time as
the tear line, and therefore may either be generated at the time of creation or during the first "export" processing.

4. Seen-by Lines

There can be many seen-by lines at the end of Echomail messages. They
are used to determine the systems that are to receive the exported messages. The format of the line is:

SEEN-BY: 132/101 113 136/601 1014/1

The net/node numbers correspond to the net/node numbers of the
systems having already received the message. In this way a message is never sent to a system twice. An Echomail system must NEVER send a
message to a system that is already in the SEEN-BY line(s).

The line is added if it is not already a part of the message.

5. PATH Lines

These are the last line(s) in a Echomail message. It appears as
follows:

^aPATH: 132/101 1014/1

Where the ^a stands for Control-A (ASCII character 1) and the
net/nodes listed correspond to those systems having processed the
message before it reached the current system. This is not the same as
the seen-by lines, because those lines list all systems the message
has been sent to, while the path line contains all systems having
actually processed the message.

METHODS OF SENDING ECHOMAIL

Each message exported from an Echomail area has one message generated
for each receiving system. This mail is then sent the same as any
other network mail.

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