Moxa Technologies 5600 - Manual (Page 24)

NPort 5600 Series User’s Manual Choosing the Proper Operation Mode
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 ports (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.
In addition to providing socket access, 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.
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.
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.
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