The port number of FTP, what is the default port of the FTP service?

The FTP port number is.

The port number of FTP can be changed.

The difference between the port number of FTP is a data port and a control port, the control port is generally 21, and the data port is not necessarily 20, which is related to the application mode of FTP, if it is active mode, it should be 20, if it is passive mode, it is determined by the negotiation between the server and the client.

Port 21 is mainly used for FTP (file

transfer

Protocol, File Transfer Protocol) service, FTP service is mainly used to achieve file upload and ** between two computers, one computer as an FTP client, another computer as an FTP server, you can use anonymous login and authorized username and password login two ways to log in to the FTP server.

An active mode FTP connection is established by following the following steps:

The client opens a random port (port number greater than 1024, here we call it x) and an FTP process connects to the server's command port 21. At this point, the source port is random port x, on the client, and the remote port is 21, on the server.

The client starts listening on port (x+1) and sends a port command to the server (via command port 21 of the server) that tells the server the port number that the client is listening on and is ready to receive data from this port. This port is what we know as a data port.

The server opens source port 20 and establishes a connection to the client data port. In this case, the source port is 20 and the remote data port is (x+1).

The client establishes a connection to the server's port 20 through the local data port, and then sends a reply to the server telling the server that it has established a connection.

21 ports for connection and 20 ports for data transfer.

In FTP file transfer, the client first connects to port 21 of the FTP server for user authentication, and after successful authentication, the server will open a port 20 to transfer data files when the file is transferred.

In other words, port 20 is the port used for the actual transmission, and port 21 is only used for FTP login authentication. When we usually **file**, we will encounter **to 99% of the time, the file is not completed and cannot be successful**. In fact, it is because after the file is completed, the user authentication must be carried out on port 21, and if the file time is too long, the connection between the client and port 21 of the server will be considered by the server to be a timeout connection and interrupted, which is the reason.

The solution is to set the response time for port 21.

1. First, double-click "My Computer" on the desktop of the computer to open the disk dialog box, and then enter the FTP server IP address in the "Path Bar" above the disk.

2. Then enter your username and password in the pop-up authentication port.

<> demo model: Huawei MatebookX system version: Win10FTP service default port is 21.

On the Internet, common services have default port numbers. Port 80 is used for HTTP-based web services; Port 21 for FTP service; Port 23 for telnet services; Port 25 is used for e-mail services.

control end: 21; Data segments: 20; Default is 21

FTP allows users to communicate with another host by means of file operations (such as adding, deleting, modifying, searching, transferring, etc.

However, instead of actually logging into the computer they want to access, the user becomes a full user, and can use the FTP program to access remote resources, transfer files to and from the user, manage directories, access e-mail, etc., even though the two computers may have different operating systems and file storage methods.