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Requirements:
=============

1. libevent >= 1.1

Available at http://www.monkey.org/~provos/libevent. Download and install this
library first.

To build libiecsock, type

$ ./configure && make

or

$ ./configure --prefix=/prefix/to/install && make

iecsock library:
================

iecsock library is an IEC 870-5-104 link layer implementation for Linux.
Though, it is not tested on FreeBSD/NetBSD, supposed to be easily ported to 
these OSes. libevent is ported to M$ platforms to. Seems being possible to make 
iecsock working on M$ Windoze (any one really needs this feature?).

It means that library handles everything related with connection and session
management, described in IEC 870-5-104 specification. User simply registers
master or slave sessions, sets default or session specific hooks on events he
is interested and receives ASDUs. User can initiate ASDUs transmission on events
or by registred timer (see client and server sources). All link layer parameters
of IEC 870-5-104 is under user control. It is possible to set timer values 
(T0-T3) and window sizes (w and k) if default values are not desirable.

iecsock library input/output is based on libevent by Niels Provos and other 
contributors (http://www.monkey.org/~provos). Threading is evil! iecsock concept
is based on asynchronous events, non-blocking I/O and a single thread of 
control. Many master and slave sessions can be registered via iecsock_connect() 
and iecsock_listen(). It is user's responsibility to provide callbacks for at 
least on data_indication to receive data. User can also register specific 
callbacks for particular iecsock session via iecsock_set_hooks().

iecasdu library:
================

iecasdu library is a work-in-progress IEC 870-5-104 ASDU parsing and creation
library implementation. This library is used to handle ASDUs and to retrieve
values, associated with them easily and in standartized form. Library can handle
variable Information Object Address and Common Address of ASDU, sequenced and
not sequenced frames (SQ=1 and SQ=0). iecasdu library represents parsed ASDU's
information objects as an array of iec_object structures. Each element of array
has address and corresponding values and very easy to use later by another 
procedures.

New information objects are very easy to add. Examine source code for example.

Currently parsing of this types of information objects is implemented:

M_SP_NA_1 - single point information
M_BO_NA_1 - 32 bitstring information state and change
M_ME_NA_1 - normalized measured value
M_ME_NB_1 - scaled measured value 
M_ME_NC_1 - short floating point measured value 
M_SP_TB_1 - single point information with CP56time2A time tag
M_BO_TB_1 - 32 bitstring information state and chane with CP56time2A time tag
M_ME_TD_1 - normalized measured value with CP56time2A time tag
M_ME_TE_1 - scaled measured value with CP56time2A time tag
M_ME_TF_1 - short floating point measured valye with CP56time2A time tag

Note, that this is a work in progress.

Testing and playing:
====================

You can run tests with client (slave side) and server (master side) programs.

$ ./bin/client

Starts IEC 870-5-104 slave and waits for master side connection. Slave can
accept and handle many master-side connections simultaneousely. Debugging
information is written to stderr.

$ ./bin/server 172.20.48.124

or 

$ ./bin/server

Starts IEC 870-5-104 master and tries to connect to slave supplied IP address
or to localhost if no arguments supplied. If slave host is not available or
closes connection because of error or any other reason, master stays persistent
and tries to reconnect after 30 seconds (T0 timer). Debugging information is
written to stderr.

Both utilities begin to exchange with I-frames filled with fixed pattern data. 
Session and frame variable fields are printed out.

Acknowledgements:
=================

None at this time.