Terminal and Print Servers --
Traditional Applications
Despite many of the
advancements of the computer industry, there still exist a great many
applications where serial I/O devices are the best or only solution.
Terminal/print/serial servers have long been the best method for
networking simple terminals, bar code readers, scanners or printers.
Input devices attached to a serial port on a server can reach any host
supporting the same protocols as that server. Printers can be shared
over the network in the same manner, with a job from one protocol
following a job from another. In the case of the print server that has
multiple ports, jobs coming from hosts supporting different protocols
can even print simultaneously.
Traditionally,
terminal/print servers have been larger, multiport devices. But as the
marketplace demands that singular devices in remote locations are
networked and as technology has developed to allow for single-port
device servers to be economically feasible, these smaller servers now
provide this remote connectivity. Single port device servers are now
being used to provide network connectivity for devices such as bar code
readers, factory automation devices, security/monitoring devices and
medical devices. This type of technology has been labeled device server
technology by industry analysts. For nearly 10 years, Lantronix has been
a leader in terminal/print server technology and has been an innovator
in the area of micro print server and single-port device server
technology. Lantronix is now on the forefront of device server
technology for the purpose of networking devices previously not on the
network.
Serial-to-Ethernet Service
For many devices, the only
access available to a network manager or programmer is via a serial
port. The reason for this is partly historical and partly evolutionary.
Historically, Ethernet interfacing has usually been a lengthy
development process involving multiple vendor protocols (some of which
have been proprietary) and the interpretation of many RFCs. Some vendors
felt Ethernet was not necessary for their product which was destined for
a centralized computer center - others felt that the development time
and expense required to have an Ethernet interface on the product was
not justified. From the evolutionary standpoint, the networking
infrastructure of many sites has only recently been developed to the
point that consistent and perceived stability has been obtained - as
users and management have become comfortable with the performance of the
network, they now focus on how they can maximize corporate productivity
in non-IS capacities.
Device Server™ technology
solves this problem by providing an easy and economical way to connect
the serial device to the network. Let's use the Lantronix MSS1-T Device
Server as an example of how to network a RAID controller serial port.
The user (or network manager) simply cables the MSS1-T's serial port to
the RAID controller's serial port and attaches the MSS1-T's Ethernet
interface to the network. The Lantronix server, once it has been given
the necessary configuration information, now makes that serial port a
networked port, with its own IP address. The user is now free to connect
to the MSS1-T's serial port from a network device (a PC or terminal
emulation device) and perform the same commands as if he were a PC
directly attached to the controller. Having now become network enabled,
the RAID controller can be managed or controlled from anywhere on the
network or via the Internet.
The key to network enabling
any device is in a server's ability to handle two separate areas: (1)
the connection between the serial device and the server and (2) the
connection between the server and the network (including other network
devices). Terminal, print and serial servers have been developed over
the years specifically for the tasks of connecting terminals, printers
and modems to the network and making those devices available as
networked devices. As current demands for networking other devices
increases, these servers need to become more generic in their handling
of the attached devices. Additionally, they will have to become even
more flexible in the manner in which they provide network connectivity.
Device Server Technology
Dataquest has described a
device server to be "a specialized network-based hardware device
designed to perform a single or specialized set of functions with client
access independent of any operating system or proprietary protocol."
Terminal, print and recently one-port terminal servers (Lantronix calls
them Device Servers) have come to embody this notion of independence
from proprietary protocols and the ability to meet a number of different
functions. The RAID controller application discussed above is just one
of many applications where these Device Servers can be used to put any
device or "thing" on the network. The recent development of the single
port Device Server now makes it economically possible to connect even
single devices with serial ports to network - prior to this development,
users had only multiport solutions which were sometimes too expensive
when the serial devices were very far apart.
Someone might ask the
question, "But haven't dedicated PCs been used to network some serial
devices with success?" The answer to this would be a somewhat qualified
yes - qualified because it required the designer of the product with the
serial port to have software able to run on the PC and then have that
application software allow the PC's networking software to access the
application. This task would be somewhat akin to the problems of putting
Ethernet on the serial device itself! To be successful, a device server
must provide a simple solution for networking a device and allow access
to that device as if it were locally available through its serial port.
Additionally, the device server should provide for the multitude of
connection possibilities that a device may require on both the serial
and network sides of a connection. Should the device be connected all
the time to a specific host or PC? Are there multiple hosts or network
devices that may want or need to connect to the newly-networked serial
device? Are there specific requirements for an application which
requires the serial device to reject a connection from the network under
certain circumstances? The bottom line is a server must have both the
flexibility to service a multitude of applications requirements and be
able to meet in depth the demands of those applications.
Lantronix Device Servers
Lantronix has been in the
terminal, print and serial server technology business for over 10 years.
During that time, Lantronix servers have been shipped worldwide and
implemented in many different applications. This experience has allowed
Lantronix to develop more functionality in our servers that "crosses the
boundary" of what many would call traditional terminal or print
services. The ability to translate between different protocols to allow
non-routable protocols to be routed; the ability to allow management
connections to single-port servers while they are processing
transactions between their serial port and the network; and the ability
to offer a wide variety of options for both serial and network
connections including serial tunneling and automatic host connection
make these servers some of the most sophisticated Ethernet-enabling
devices available today. By virtue of the ability to network almost any
serial device, Lantronix has termed our server technology, Device Server
Technology.
Let's take a look at a
particular example of how Device Servers can be used. Mainframe
computers and high-end workstations present a particular management
problem in networked environments because they normally reserve a number
of critical configuration and management parameters for a serial console
port device. The ability to reconfigure system memory, allocate disk
resources and build system features are reserved for this console which
is assumed to be located in a safe and secure environment (generally a
centralized computer room). For the network manager who uses principally
networked management tools, the challenge is how does this person manage
this type of device? The answer to this question lies in using a
universal device server as a console server - by connecting the Device
Server's serial port to the console port of the workstation, the network
manager can now exercise the full range of console commands from
anywhere on the network. The Device Server allows the serial port of the
workstation to now become a networked port, reachable via connection to
the Device Server's IP address. In this manner, the network manager can
connect from any device supporting the IP protocol to the workstation's
console port and then can execute the commands normally reserved for
that port. The result is that any workstation or mainframe system can
therefore be managed over the network as if the network manager were in
the central computer room where the console of the system was located.
A user might say at this
point that the use of the Device Server in this application is very much
like that of the common terminal server. But if one just takes a
standard terminal server and puts it in this application, will they be
successful? The answer is that they may not. With a console server, you
would want to have ways of grabbing a port's attention if it should be
hung - this would mean that you would want some kind of comprehensive
management function available to you should a connection appear to be
faulty. Additionally, you would want some kind of diagnostic information
to ascertain if there was network problem or a serial port problem if
the connection was not working as expected. Thirdly, the interface to
the console might require some special break or control character or
even modem signal to be sent to wake up the console or initiate a
particular management feature. Lastly, there might be a compatibility
requirement with a host-based application program that places severe
limitations on how the network connection from the host to the server
will take place. The fact is that many of these features may not be
available in a standard terminal server and knowing that the lack of any
one of them might mean that a particular console could not be networked
would lead to a rejection of the proposed server as a solution.
Lantronix engineers have
spent the last decade developing the widest possible variety of
applications for our server products. One example of this is in the
development of a Windows 95/98 and Windows NT program that maps a PC's
serial ports to it's network port(s). What this software provides is the
ability to take the application software developed for a serial port on
a PC and allow that software to be run on a networked PC. That networked
PC can now connect to the device attached to the serial port of the
Lantronix Device Server as if it were on the PC's serial port. This
means that any device with a serial port with a dedicated PC can now
become a network device with the ability of a PC anywhere on the network
(or the Internet) to manage it. From the start of the network enabling
process, there is no need to modify any applications software in the PC
to be able to access the Lantronix server's serial port (with serial
device attached) from anywhere on the network. This feature is called
application transparency.
By virtue of being an
independent device on the network, one might think that management of a
Device Server might be a problem - nothing could be farther from the
truth. As stated before, Lantronix has spent over 10 years perfecting
our Ethernet protocol software and Lantronix engineers have provided a
wide range of management tools for this device server technology. Since
terminal servers and serial servers have serial ports it makes sense
that these ports can also be used for management purposes - a simple
command set allows easy configuration in this manner. The same command
set that can be exercised on the serial port can be used when connecting
via telnet to a Lantronix device server. An important feature to
remember about the Lantronix telnet management interface is that it can
actually be run as a second connection while data is being transferred
through the server - this feature allows the user to actually monitor
the data traffic on even a single-port server's serial port connection
while active. The Lantronix Device Servers also support SNMP, the
recognized standard for IP management that is used by many large network
for management purposes. And finally, Lantronix has it's own web-based
management tool, EZWebCon, a graphical user interface which provides the
easiest way to manage the Lantronix Device Servers. In addition to these
features, the servers all have Flash ROMs, which can be reprogrammed in
the field by download. Many new small device server products do not have
this feature. This means that new software might have to be downloaded
over the serial port or simply not at all. Lantronix was one of the
pioneers of providing software upgrades for free over the Internet and
the Lantronix web site (www.lantronix.com) guides the user through the
process with ease.
Device Servers - Making the
Applications Work
We have looked at why
organizations are looking for Device Servers and we have seen one
example of it in the area of console service and we described what
device server technology should be. But the real test is - does a device
server provide all of the features required to network enable the
application successfully? We are going to look at a few applications
areas in which there is a great deal of interest in device server
technology and how Lantronix Device Servers facilitate those
applications.
Data Acquisition
Microprocessors have made
their way into almost all aspects of human life, from automobiles to
appliances to even hockey pucks. With so much information out there to
be gathered, it stands to reason that an organization or individual will
want to collect as much of it as fast as possible. Although some data
acquisition devices use a serial interface, there are a wide variety of
other interfaces to support these devices. One such standard is RS-485.
Designed to allow for multiple devices to be linked by a multidrop
network of RS-485 serial devices, this standard also had the benefit of
greater distance than offered by the RS-232/RS-423 and RS-422 standards.
Many of these applications run in campus-type environments, so
right-of-way to lay cable between devices was available.
Because of the factors we
have previously outlined, these types of devices can benefit from being
network enabled. Firstly, Ethernet networks have a further range than
many serial technologies. Secondly, Ethernet protocols actually monitor
packet traffic and will indicate when packets are being lost compared to
serial technologies which do not guarantee data integrity. Lantronix's
full family of Device Server products provides the full gamut of support
required for network enabling different serial interfaces. In
particular, the MSS485-T serial servers support RS-485 and allow for
easy integration of these types of devices into the network umbrella.
For RS-232 or RS-423 serial devices, the MSS1 and MSS100 products can be
used to connect sensors to either Ethernet or Fast Ethernet. The
Lantronix terminal server products offer multiport configurations for
those sites where multiple sensors may be in close proximity.
But this is just the
beginning of the support that may be required for critical applications.
Say that a number of data acquisition devices monitor the temperature of
a furnace - it stands to reason that any prudent user would want to
ensure themselves of making sure these sensors are always working and
working correctly. The answer here is that Lantronix's universal device
servers have several features that enable this application to work
efficiently and correctly. To verify that a sensor and its server is
transmitting, a user could set up a ping application using the IP
protocol to sound that unit every second or so - this would validate the
existence and operational capability of the data device. Still using IP,
the Lantronix device server could be programmed to transmit data to
separate IP addresses on the network for cross-checking or validation at
different management stations. These features, standard to Lantronix
device servers, may not be found on other products being offered for
data acquisition applications.
Factory Floor Automation
For factories that are
running automated assembly and manufacturing applications, time is
money. For every minute a device is idle, productivity will decrease.
Many automated factory floor devices have either serial ports or require
a dedicated PC to program them. In some cases, handheld PCs are used to
reprogram devices for different functions. These devices could be
networked to allow them to be reprogrammed over the network, saving time
and money. From a central location or actually from anywhere in the
world with network connectivity, new device programs can be downloaded.
One item of interest is how
that input programming is formatted. We have reviewed how the Lantronix
device servers have a port redirector software package to provide
application transparency, but since many of these automation devices are
legacy or proprietary, any number of different data streams could be
used. Lantronix device servers have the ability to set up their serial
ports for virtually any kind of data transaction. In the IP environment,
this includes the ability to support telnet connects or telnet connects
without IAC negotiation (raw sockets). Additionally, all Lantronix
device servers can support binary character transmissions. In these
situations, the need for possible flow control may arise and Lantronix
has accounted for this need by supporting RTS/CTS flow control on our
DB25 and RJ45 ports. So be it a simple ASCII command file or complex
binary program that needs to be transmitted to a device, Lantronix
device servers can do the job.
Security Systems
One area that every
organization is concerned about is security. Card readers are
commonplace now and these type of devices are good candidates for device
server technology - when networked to a central system, there will be
records of all access within the organization. Newer technology includes
badges that can be scanned from a distance of up to several feet and
biometric scanning devices that can identify an individual by a
thumbprint or handprint. device servers allow these types of devices to
be placed throughout an organization's network and allow them to be
effectively managed by a minimum staff at a central location.
One more area of security
systems that has made great strides is in the area of security cameras.
In some cases, local municipalities are now requesting that they get
visual proof of a security breach before they will send authorities.
Lantronix device server technology provides the user with a host of
options for how such data can be handled. One option is to have an open
data pipe on a security camera - this allows all data to be viewed as it
comes across from the camera. The device server can be configured so
that immediately on powerup the serial port attached to the camera will
be connected to a dedicated host system. Another option is to have the
camera transmit only when it has data to send. By configuring the device
server to automatically connect to a particular site when a character
first hits the buffer, data will be transmitted only when it is
available. One last option is available when using the IP protocol -
Lantronix device servers can be configured to transmit data from one
serial device to multiple IP addresses for various recording or archival
concerns. Lantronix device server technology gives the user many options
for tuning the device to meet the specific needs of their application.
Scanning Devices
Scanning devices such as
bar code readers or debit card scanners are another application where
device server technology can be effectively applied. When a bar code
reader is located in a remote corner of the warehouse at a receiving
dock, a single-port server can link the reader to the network and
provide up-to-the-minute inventory information. A debit card scanner
system can be set up at any educational, commercial or industrial site
with automatic debiting per employee for activities, meals and
purchases. A popular amusement park in the United States utilizes such a
system to deter theft or reselling of partially-used admission tickets -
by having no distinguishing marks other than the person's name and a
barcode on the card, the black market for partially-used tickets has
been greatly reduced.
Lantronix's device server
technology simplifies these types of applications with a feature called
autostart. Once the reader or scanner is powered on, it will remain on
permanently for a predetermined length of time, the device server to
which the serial port of the reader/scanner is attached will
automatically open a connection to a specified host upon powerup of the
unit. This connection will remain open as long as the user wishes,
capable of supporting any amount of continuous transactions. If the
attached scanner is one which is only going to be used for a short
period of time, then the Lantronix device server can be configured for
both preferred connection and dsrlogout - this combination will
terminate a connection when the attached scanner device is turned off
but still retain the ability to make an automatic connection to the
specified host when the scanner begins operations again.
Medical Devices
Medical devices are another
area where device server technology can provide great flexibility and
convenience. Many medical organizations now run comprehensive
applications developed specifically for their particular area of
expertise. For instance, a group specializing in orthopedics may have
x-ray and lab facilities onsite to save time and customer effort in
obtaining test results - connecting all the input terminals, lab
devices, x-ray machines and developing equipment together allows for
efficient and effective service. As many of the more technical devices
previously relied upon serial communication or worse yet, processing
being done locally on a PC, then so device server technology can be used
to link them all together into one seamless application. Of course,
Internet connection allows the physicians to take advantage of any new
information relevant to their pursuits.
Larger medical labs, where
there are hundreds of different devices available for providing test
data, can greatly reduce their workload by using device server
technology to replace dedicated PCs at each device. At first glance,
this might seem like a tradeoff given the cost of a device server and
the cost of a PC - but think not of the hardware alone, think of the
man-hours required to create software that would allow a
PC-serial-port-based applications program to be converted into a program
linking that information to the PC's network port. A Lantronix device
server can resolve this issue by allowing the original applications
software to be run on a networked PC and then use port redirector
software to connect up to that device via the network. Where originally,
there was a PC at each device and software development required to
network that data, now there is only a couple of high-end networked PCs
doing the processing for all of the devices.
So Many More Applications
There obviously are many
more applications where device server technology can be used - some as
mundane as vending machines' inventory monitoring and others as critical
as rocket launch pad telemetry data collection. The point is the move is
on to migrate as many things as possible on the network. As we have also
seen, applications support may require more than just simply getting an
IP address for a device - it may require special handling of the flow
control or data characteristics of the serial port, it may require
special processing during the transfer to the network and it may require
special management abilities far beyond a simple telnet capability.
Lantronix has been an industry leader for over a decade in the terminal,
print and serial server business and as these applications-specific
servers are being called, device servers. Examine the Lantronix products
that you can find by choosing 'Lantronix Products' below and you will
find products that will both meet and exceed your applications
requirements in both performance and price.
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