[Service]ftp active mode and passive mode

Often forget this thing. So summarize this thing and feel the agreement.

• FTP connection mode
  • Control connection: Standard port, for sending FTP command information
  • Data connection: Standard port, for uploading and downloading data
  • Type of data connection establishment:
    • Active mode: the server initiates a connection from Port 20 actively to the client
    • Passive mode: The server is passively waiting for a client to initiate a connection at a port within a specified range
• FTP transfer Mode
  • Text mode: ASCII mode, transferring data in a text sequence
  • Binary mode: Binary mode, transferring data in binary sequence

Summarize:

a  

Two stages: Control connection TCP ( Client initiated, three handshake process)

? Data connection TCP(optional)

Two

FTP establish the connection process :

1, Control Connection :--- establish a control connection first : Clinet take the initiative to Server three-time handshake .

2, Data Connection :

data plane:

Active mode:FTP Server actively uses its own Port as the source side to connect the FTP client. --------- applicable firewall

Passive mode:FTP server tells the client I opened the port, you can even me. --------- Firewall Not applicable

Note : Active mode and passive mode are discussed in the second phase . .

Note : Firewall Environment Applicable FTP Active mode. ?

There are two ways to establish a data connection:

Active mode: Data connection : Server Active to sport20 to connect Client . the client said, I opened the 1049, you come to connect me.

Active mode resolves firewall issues.

Passive mode: I take my 1089 to connect A I take my 1090 to connect B .

xftp The default is to connect in passive mode. In general, we use passive mode. However, if you encounter a firewall, you need to use active mode.

[Service]ftp active mode and passive mode