Data exchange has been important from the early days of computing. A
popular means of data exchange is connecting computers to one another.
The File Transfer Protocol (FTP) is used to transfer files
between two computers over a network and Internet. In this article we
will look at how to work with FTP a client.
When you want to copy files between two computers that are on
the same local network, often you can simply "share" a drive or folder,
and copy the files the same way you would copy files from one place to
another on your own PC.
What if you want to copy files from one computer to another that
is halfway around the world? You would probably use your Internet
connection. However, for security reasons, it is very uncommon to share
folders over the Internet. File transfers over the Internet use special
techniques, of which one of the oldest and most widely-used is FTP. FTP, short for "File Transfer Protocol,"
can transfer files between any computers that have an Internet
connection, and also works between computers using totally different
operating systems.
Transferring files from a client computer to a server computer is called "uploading" and transferring from a server to a client is "downloading".
Requirements for using FTP
To transfer files, provide your client software (Auto FTP Manager) with the server address, user name, and password. After connecting to the FTP server, you can use Auto FTP Manager's File Manager to upload, download and delete files. Using the File Manager is a lot like working with Windows Explorer.
FTP and Internet Connections
FTP uses one connection for commands and the other for sending
and receiving data. FTP has a standard port number on which the FTP
server "listens" for connections. A port is a "logical connection point"
for communicating using the Internet Protocol (IP). The standard port
number used by FTP servers is 21 and is used only for sending commands.
Since port 21 is used exclusively for sending commands, this port is
referred to as a command port. For example, to get a list of
folders and files present on the FTP server, the FTP Client issues a
"LIST" command. The FTP server then sends a list of all folders and
files back to the FTP Client. So what about the internet connection
used to send and receive data? The port that is used for transferring
data is referred to as a data port. The number of the data port will vary depending on the "mode" of the connection. (See below for Active and Passive modes.)
The FTP server may support Active or Passive connections,
or both. In an Active FTP connection, the client opens a port and
listens and the server actively connects to it. In a Passive FTP
connection, the server opens a port and listens (passively) and the
client connects to it. You must grant Auto FTP Manager access to the
Internet and to choose the right type of FTP Connection Mode.
Most FTP client programs select passive connection mode by
default because server administrators prefer it as a safety measure.
Firewalls generally block connections that are "initiated" from the
outside. Using passive mode, the FTP client (like Auto FTP Manager) is
"reaching out" to the server to make the connection. The firewall will
allow these outgoing connections, meaning that no special adjustments to
firewall settings are required.
If you are connecting to the FTP server using Active mode
of connection you must set your firewall to accept connections to the
port that your FTP client will open. However, many Internet service
providers block incoming connections to all ports above 1024. Active
FTP servers generally use port 20 as their data port. It's a good idea
to use Passive mode to connect to an FTP server. Most FTP servers
support the Passive mode. For Passive FTP connection to succeed, the
FTP server administrator must set his / her firewall to accept all
connections to any ports that the FTP server may open. However, this is
the server administrator's problem (and standard practice for servers).
You can go ahead, make and use FTP connections.
Once the FTP Client manages to open the internet connections,
one for command and one for data, it starts communicating with the FTP
server. You are now ready to transfer your files and folders between the
two connected computers.
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