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NPort 5110 Series User’s Manual Choosing the Proper Operation Mode
4-2
Overview
NPort 5110 Serial Device Servers are used to network-enable traditional RS-232 devices. A Serial
Device Server is a tiny computer equipped with a CPU, real-time OS, and TCP/IP protocols that
can bi-directionally transfer 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) to collect data from
various kinds of instruments. Since NPort 5110 Serial Device Servers network-enable instruments
equipped with an RS-232 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 5110 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 5110 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 data to be unicast or
multicast to only one IP or to different groups of IP addresses.
TCP Server Mode
In TCP Server mode, NPort 5110 is configured with a unique IP:Port address on a TCP/IP network.
NPort 5110 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 5110 configured for TCP Server Mode.
2. Once the connection is established, data can be transmitted in both directions—from the host
to the NPort 5110, and from the NPort 5110 to the host.
TCP Client Mode
In TCP Client mode, NPort 5110 can actively establish a TCP connection to a pre-defined host
computer when serial data arrives.
After the data has been transferred, NPort 5110 can automatically disconnect from the host
computer by using the TCP alive check time or Inactivity time settings. Refer to Chapter 5 for
more details.
Data transmission proceeds as follows:
1. The NPort 5110 configured for TCP Client Mode requests a connection from the host.
2. Once the connection is established, data can be transmitted in both directions—from the host
to the NPort 5110, and from the NPort 5110 to the host.