User's Manual Part 1

NPort W2004 User’s Manual Choosing the Proper Operation Mode
4-2
Overview
NPort W2004 wireless Serial Device Servers are used to network-enable traditional
RS-232/422/485 devices. A Serial Device Server is a tiny computer equipped with a CPU,
real-time OS, and TCP/IP protocols that can bi-directionally translate data between the serial and
Ethernet formats. The Serial Device Server lets you use a computer to access, manage, and
configure remote facilities and equipment over the Internet from anywhere in the world.
Traditional SCADA and data collection systems rely on serial ports (RS-232/422/485) to collect
data from different types of instruments. Since NPort W2004 wireless Serial Device Servers
network-enable instruments equipped with an RS-232/422/485 communication port, your SCADA
and data collection system will be able to access all instruments connected to a standard TCP/IP
network, regardless of whether the devices are used locally or at a remote site.
NPort W2004 is an external IP-based network device that allows you to expand the number of
serial ports for a host computer on demand. As long as your host computer supports the TCP/IP
protocol, you won’t be limited by the host computer’s limited number of conventional busses
(such as ISA or PCI), or lack of drivers for various operating systems.
In addition to providing socket access, NPort W2004 also comes with a Real COM/TTY driver
that transmits all serial signals intact. This means that you can continue using existing
COM/TTY-based software, eliminating the need to invest in additional, costly software.
Three different Socket Modes are available: TCP Server, TCP Client, and UDP Server/Client. The
main difference between the TCP and UDP protocols is that TCP guarantees delivery of data by
requiring the recipient to send an acknowledgement to the sender. UDP does not require this type
of verification, making it possible to offer speedier delivery. UDP lets you unicast to one IP
address, or multicast to groups of IP addresses.
TCP Server Mode
In TCP Server mode, NPort W2004 is
configured with a unique IP:Port address
on a TCP/IP network. NPort W2004 waits
passively to be contacted by the host
computer, allowing the host computer to
establish a connection with and get data
from the serial device.
This operation mode also supports up to 4
simultaneous connections, so that multiple
hosts can collect data from the same serial
device—at the same time.
As illustrated in the figure, data
transmission proceeds as follows:
TCP Server Mode
Request a
connection
Proceed with
data transmission
1
2
1
2
NPort W2004
TCP/IP
WLAN
RS-232
Console
Device Serv
er
NPort W2004
WLAN
P1
P3
P2
P4
P1
P2
P3
P4
Signal
Strength
Ready
RS-232/422/485
Ethernet
Serial (TTL)
Serial Device
1. The host requests a connection from the NPort W2004 configured for TCP Server Mode.
2. Once the connection is established, data can be transmitted in both directions—from the host
to the NPort W2004, and from the NPort W2004 to the host.