Moxa Technologies 5400 - Manual (Page 24)

Overview
NPort Device Servers network-enable traditional RS-232/422/485 devices, in which a 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. Your computer can 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 prots (RS-232/422/485) to collect data
from various kinds of instruments. Since NPort 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 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 bus limitation (such as ISA or PCI), or lack of drivers for various
operating systems.
In addition to providing socket access, NPort also comes with a Real COM/TTY driver that transmits
all serial signals intact. This means that your existing COM/TTY-based software can be preserved,
without needing to invest in additional 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 also allows multicasting of data to
groups of IP addresses.
Pictures in this Chapter will use NPort 5400 series as an example.
TCP Server Mode
In TCP Server mode, NPort provides a unique IP:Port address
on a TCP/IP network. NPort 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:
1. The host requests a connection from the NPort configured
for TCP Server Mode.
2. Once the connection is established, data can be
transmitted in both directions—from the host to the
NPort, and from the NPort to the host.
NPort 5400 Series User’s Manual 4-2