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.
RealCOM 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
non-critical 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.
RealCOM Mode
RealCOM
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.
RealCOM
mode supports up to four
simultaneous connections, so multiple hosts can
collect data from the attached device at the same
time.
ATTENTION
RealCOM
drivers are installed and configured through NPort Windows Driver Manager.
RealCOM 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 RealCOM 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.