Configuration Guide FTP Client Configuration
FTP Client Configuration
FTP Client provides users with the feature of file transfer with remote FTP server through FTP protocol.
FTP Overview
FTP (File Transfer Protocol) is a concrete application of TCP/IP for establishing connection-oriented and reliable TCP
session between FTP client and server. The user can access a remote computer running FTP server program. After the
user issues commands to the server, the server will respond to such commands and return the execution results to the
client. Through such command interaction, the user can view files under the server directories and copy such files from
remote computer to the local device, or transfer the local files to the remote computer. FTP protocol is detailed in RFC
959.
FTP Connection Mode
FTP maintains two TCP connections:
Control link (also referred to command link) for transferring command between FTP client and server.
Data link for uploading or downloading data.
Control connection: For certain simple connections, only the control connection is needed. The client sends commands to
the server, which will then respond to these commands. The process is shown below:
Figure 1 Control Connection
Control connection and data connection: When the client needs to upload or download data, the data connection must be
established in addition to the control connection.
FTP features to two types of data connections: active (PORT) mode and passive (PASV) mode. The key difference
between them is the mode of data connection establishment, yet they are basically the same in terms of control
connection establishment.
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