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| In this section, we give brief definitions of several important networking terms and acronyms. |
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| API |
An Application
Programming Interface is a series of functions that programmers
use to communicate with network protocol suites. Functions
include establishing a connection, reading or writing data,
and disconnecting from the network. |
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| client program |
| A client program is a type of computer program that actively requests service from a server program, which often resides on another computer. |
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| COM port |
| A COM port is a serial communications port (RS-232 interface) on a Windows-based PC. Most PCs come with two built-in COM ports, although the number of ports can be extended into the hundreds by installing either multiport serial boards, or network-based serial device servers. |
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| cross-over cable |
| A cross-over cable is used
to connect two ports of like nature. A serial cross-over
cable is used to connect a DCE device to a DCE device (or
a DTE device to a DTE device). An Ethernet cross-over cable
can be used to connect two NIC cards installed in two different
computers without using an Ethernet hub or switch. |
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| Data-stream transmission |
| Data-stream transmission refers to a series of data transmitted continuously without interruption. |
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| Ethernet |
| Ethernet is a local-area
network architecture developed by Xerox, DEC, and Intel in
1976. It operates using a shared bus or star topology, and
supports data transfer rates of 10 Mbps, 100 Mbps, and 1000
Mbps. |
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| Ethernet frame |
| An Ethernet frame is a packet
of data bits sent from one device to another over an Ethernet network. |
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| fixed tty driver |
A fixed tty driver is a driver
program used by Unix/Linux systems to control external devices
connected to the serial device server's serial port(s). Fixed
tty drivers are characterized by the fact that a user's
software is able to transmit data via a pseudo tty port based
on pre-defined communication
parameters, making them suitable for pure data transmission. However, the
user's software cannot be used to change a port's communication parameters.
The limitation is that the user's software is not able to control
DTR, RTS, and DCD signals during operation. Another kind of tty driver,
a real tty driver, supports full serial port control functions. |
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| host |
| A host is a computer, such as a PC or Linux server, that is connected to a network. Each host is assigned its own unique IP address. |
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| HTML |
| HTML (HyperText Markup Language) is
the computer language used to produce text files that contain
typesetting commands that allow the
document to be viewed with a web browser (such as Netscape® or
Internet Explorer®). HTML defines the structure of tags
and attributes used to create Web text documents. |
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| HTTP |
| HTTP (HyperText Transfer Protocol) defines how messages are formatted
and transmitted, and what actions the Web server should take. |
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| hub |
| A hub is a device
with several Ethernet ports and an internal mechanism to
retransmit received
packets to all ports except the receiving port. In general,
a hub does not filter packets or incorporate any kind of
learning system to restrict transmission to specific ports.
Compare switch. |
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| IP address |
| An IP address is a 32-bit
identification number assigned to networking devices connected
to a TCP/IP network such as the Internet. IP addresses are
written in the form 192.168.206.10 (see also public
IP address and private IP address). |
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| LAN |
| A LAN (Local Area Network) is a computer
network for which messages sent from one LAN computer to
another does not pass through a router. Most LANs
are located
within a relatively small
geographical area, such as a building or campus. |
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| multidrop network |
| A multidrop network, which is a type of computer network that allows several
devices to communicate over the same pair of wires, is usually associated with
the RS-485 serial interface. In a multidrop network, one node can broadcast
data to all other nodes at the same time. |
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| netmask |
| A netmask is a 32-bit number
used to determine the network scope of a computer's
IP address. The most commonly used netmasks are 255.0.0.0
for Class A networks, 255.255.0.0 for Class B networks, and
255.255.255.0 for
Class C networks. For example, a computer with IP address
192.168.254.15 and netmask 255.255.255.0 belongs to a Class
C network, in which all
computers on the network have IP addresses of the form 192.168.254.xxx. |
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| protocol suite |
| A protocol suite is a collection of protocols used for device-to-device communication
over a network. The TCP/IP protocol suite, for example, is composed
of protocols such as TCP, IP, UDP, ICMP, ARP, etc. |
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| Real COM driver |
| A Real COM driver is a driver
program under Windows that emulates the behavior of a local
COM port. The driver is used for ports on a
serial device server that connects to the host via
a TCP/IP network. The serial port on the remote serial device
server will exhibit the same behavior as a local COM
port. A router is a network device that is used to connect
two
or more LANs or WANs via a leased line, ADSL, or other long
distance communications
interface. Routers are able to determine data packet destinations. |
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| Real tty driver |
| A real tty
driver is
a driver program used by Unix/Linux systems to control external
devices connected to the serial device server's serial port(s).
Real tty
drivers are characterized by the fact that a user's
software is able to transmit data by standard tty interfaces.
It allows you to perform full
tty interface functions, including
data transmission, and line signal control (such as RTS,
CTS, DTR, DSR, DCD, and break signal).
Another, simpler form of tty driver is
the fixed tty driver, used for pure data transmission. |
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| router |
| A router is a network device that is used to connect two or more LANs or
WANs via a leased line, ADSL, or other long distance communications
interface. Routers are able to determine data packet destinations. |
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| RS-232 |
| RS-232 is a standard interface for connecting serial devices. Many modems,
display screens, and printers are designed to operate via an RS-232 port. |
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| RS-422 |
| The RS-422 standard is based on the RS-232 standard, but is designed to
support higher data rates and longer data transmission distances (up to 1.2
km). RS-422 also has greater immunity to electrical interference. |
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| RS-485 |
| RS-485 has many of the same
characteristics as RS-422, especially in terms of
data transmission distance and immunity to electrical interference.
In addition, it supports 2-wire multi-drop operation and
allows 32 RS-485 nodes over a 2-wire bus. The 2-wire
RS-485 format is used widely for industrial control networks. |
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| serial communication |
| Serial
communication refers to the transmission of data essentially
one bit at a time. |
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| serial device server |
| A serial device server is a standalone device that has at least one Ethernet port
and one or more serial ports. Serial device servers are equipped with an
embedded network operating system and allow computers to access serial
devices over a network. |
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| serial tunnel |
| A serial tunnel is used to
encapsulate serial data in a TCP/IP packet or datagram, and
then send it over a network. Serial tunnels allow a host
computer to use a network connection to access data from
virtually any type of serial device. |
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| server farm |
| A server farm is an enterprise
that houses hundreds or thousands of server computers that
are leased to other companies. Businesses that run server
farms often provide a full range of support, from simply
leasing space for a
computer to offering professional web site design and maintenance
services. |
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| server room |
| A server room houses computers
and network equipment, and is usually climate controlled
to protect expensive electronic equipment from extreme temperatures
and dusty conditions. |
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| server program |
| A server program is a computer program that waits passively for requests for
service from client programs. |
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| socket programming |
| Socket programming refers
to scripts that execute functions that read and write
data to and from a socket. |
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| straight-through cable |
| A straight-through cable is
used to connect two ports of dislike nature. A serial straight-through
cable is used to connect a DCE device to a DTE device. An
Ethernet straight-through cable is used to connect a computer's
NIC to a hub
or switch. |
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| switch |
| In terms of network communication, a switch is an intelligent hub that
automatically identifies the direction of traffic, and isolates the traffic on
different collision domains. Switches can ensure maximum bandwidth usage
for each Ethernet connection. |
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| TCP/IP |
| The TCP/IP protocol suite refers to the family of network protocols used by
most Ethernet networks, and by the Internet, to connect hosts. TCP/IP, in which
TCP stands for Transmission Control Protocol and IP stands for Internet
Protocol, is a standard for transmitting data over networks. |
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| TCP header |
| A TCP header consists of identification and control information that is affixed
to the beginning of a TCP packet as the packet passes through the TCP/IP stack. |
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| TCP packet |
| A TCP packet consists of data and headers sent by TCP over a TCP/IP network
(compare with UDP datagram). |
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| TCP socket |
| A TCP socket is a program
that can send and receive TCP/IP messages by opening
a socket, and then reading and writing data to and from the
socket. Note that "socket" in this case is a software object,
and not a separate physical port through which data is received
and transmitted. |
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| Telnet |
| Telnet is a widely used protocol that establishes a network connection with a
networked device. Many standard software utilities are based on the Telnet
protocol, such as Telnet (system utility name) under Windows and Linux. Many
network devices, such as serial device servers and routers have a built-in Telnet
console that allows users to configure the device by the Telnet utility. |
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| UDP |
| A UDP datagram consists of data sent by UDP over a TCP/IP network (compare
with TCP packet). |
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| WAN |
| A WAN (Wide Area
Network) consists of two or more LANs connected by switches
and/or routers. |
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| WinSock |
| WinSock is the standard Windows API utility that uses TCP/IP protocol to
connect other network devices. |
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