MHB FTP Port 21: Client/Host Usage & Alternatives

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The standard port for FTP is indeed 21, which the server uses to listen for incoming connections. The client, however, typically uses an arbitrary port number, usually in the 5000+ range, for its connection. When a connection is established, the server creates a new socket on a different port in the same range to handle the communication, ensuring that port 21 remains available for new connections. This behavior can be observed using the netstat command-line utility.
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I'm reading a text that is saying that the standard port for ftp is 21.

Do both the client/host use port 21? And what is the port is already being used, does it go to a different port?
 
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tmt said:
I'm reading a text that is saying that the standard port for ftp is 21.

Do both the client/host use port 21? And what is the port is already being used, does it go to a different port?

Hi tmt,

The server listens on port 21.
Locally the client gets assigned an arbitrary port number, usually in the 5000+ range.
When a connection is made, the server usually spawns off a new socket on a new port, also in the 5000+ range.
That way port 21 on the server remains reserved for listening to new connections.

You can see this when you run the command line utility [m]netstat[/m] with the appropriate parameters.
 
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