User's Manual

NPort W2150A/W2250A Series Introduction to Operation Modes
4-2
Overview
This chapter introduces the different serial port operation modes that are available on the NPort
W2150A/W2250A Series. Each serial port on the NPort is configured independently of the other ports, with
its own serial communication parameters and operation mode. The serial port’s operation mode determines
how it interacts with the network, and different modes are available to encompass a wide variety of
applications and devices.
Real COM and RFC2217 modes allow serial-based software to access the NPort serial port as if it were a
local serial port on a PC. These modes are appropriate when your application relies on Windows or Linux
software that was originally designed for locally attached COM or TTY devices. With these modes, you can
access your devices from the network using your existing COM/TTY-based software, without investing in
additional software.
Three different socket modes are available for user-developed socket programs: TCP Server, TCP Client,
and UDP Server/Client. For TCP applications, the appropriate mode depends on whether the connection
will be hosted or initiated from the NPort serial port or from the network. 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 and would be suitable for
streaming media or noncritical messaging applications such as LED message boards.
Pair Connection Slave and Master modes are designed for serial-to-serial communication over Ethernet,
in order to overcome traditional limitations with serial transmission distance.
In Ethernet Modem mode, the NPort acts as an Ethernet modem, providing a network connection to a host
through the serial port.
Real COM Mode
Real COM mode is designed to work with NPort
drivers that are installed on a network host. COM
drivers are provided for Windows systems, and TTY
drivers are provided for Linux and UNIX systems.
The driver establishes a transparent connection to
the attached serial device by mapping a local serial
port to the NPort serial port. Real COM mode
supports up to four simultaneous connections, so
multiple hosts can collect data from the attached
device at the same time.
ATTENTION
Real COM drivers are installed and configured through NPort Windows Driver Manager.
Real COM mode allows you to continue using your serial communications software to access devices that are
now attached to your NPort device server. On the host, the NPort Real COM driver automatically intercepts
data sent to the COM port, packs it into a TCP/IP packet, and redirects it to the network. At the other end of
the connection, the NPort device server accepts the Ethernet frame, unpacks the TCP/IP packet, and sends
the serial data to the appropriate device.