owtap - Online in the Cloud

PROGRAM:

NAME

owtap - Packet sniffer for the owserver protocol

SYNOPSIS

owtap -p owtap-tcp-port -s owserver-tcp-port

DESCRIPTION

1-Wire
1-wire is a wiring protocol and series of devices designed and manufactured by Dallas
Semiconductor, Inc. The bus is a low-power low-speed low-connector scheme where the data
line can also provide power.

Each device is uniquely and unalterably numbered during manufacture. There are a wide
variety of devices, including memory, sensors (humidity, temperature, voltage, contact,
current), switches, timers and data loggers. More complex devices (like thermocouple
sensors) can be built with these basic devices. There are also 1-wire devices that have
encryption included.

The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus
master initiates all communication. The slaves can be individually discovered and
addressed using their unique ID.

Bus masters come in a variety of configurations including serial, parallel, i2c, network
or USB adapters.

OWFS design
OWFS is a suite of programs that designed to make the 1-wire bus and its devices easily
accessible. The underlying principle is to create a virtual filesystem, with the unique ID
being the directory, and the individual properties of the device are represented as simple
files that can be read and written.

Details of the individual slave or master design are hidden behind a consistent interface.
The goal is to provide an easy set of tools for a software designer to create monitoring
or control applications. There are some performance enhancements in the implementation,
including data caching, parallel access to bus masters, and aggregation of device
communication. Still the fundemental goal has been ease of use, flexibility and
correctness rather than speed.

owserver
owserver (1) is the backend component of the OWFS 1-wire bus control system. owserver (1)
arbitrates access to the bus from multiple client processes. The physical bus is usually
connected to a serial or USB port, and other processes connect to owserver (1) over
network sockets (tcp port).

Frontend clients include a filesystem representation: owfs (1) , and a webserver: owhttpd
(1). Direct language bindings are also available, e.g: owperl (3).

There are also many light-weight clients that can only talk to owserver (1) and not to the
1-Wire bus directly. They include shell and multiple language modules (perl, Visual Basic,
python,...)

owserver protocol
All the owserver (1) clients use the owserver protocol for communication. The owserver
protocol is a well documented tcp/ip client/server protocol. Assigned the "well known
port" default of 4304.

owtap
owtap (1) is interposed between owserver (1) and clients, to display and help resolve
communication problems. Network communication is forwarded in both directions, but a
visual display is also created, with statistics and "drill-down" of individual packets.

SPECIFIC OPTIONS

-p
TCP port or IPaddress:port for owtap
Other OWFS programs will access owtap via this address. (e.g. owdir -s IP:port /)

-s
TCP port or IPaddress:port for owserver
The tcp port (IP:port) for the "upstream" owserver.

EXAMPLE

If owserver (1) is started:
owserver -p 4304 -d /dev/ttyS0
owserver on tcp port 4304 and connects to a physical 1-wire bus on a serial port.

You can directly query owserver (1) with
owdir -s 4304 /

To see the protocol in action:
owtap -s 4304 -p 3000
owdir -p 3000 /

In this case owtap (1) is connecting to owserver (1) on the original port (4304) and
offering a new port (3000) for clients.

PLATFOMS

owtap (1) is a pure Tcl/TK program and will run whereever Tcl/TK is available (Windows,
Macintosh, Linux, Unix)

LINKS

owserver protocol
http://www.owfs.org/index.php?page=owserver-protocol

Tcl/TK
http://www.tcl.tk

Use owtap online using onworks.net services