File transfer protocol

Since the internet came into existence, we have been working with the file transfer protocol (FTP). FTP uses TCP over port 21 or 20 (by default) to initiate and transfer files over a designated channel. There are only two types channel command channel (port 21) and data channel (port 20). The command channel is used to send and receive the commands and their responses. The data channel is used to send and receive data between the client and the server. However, you will observe random port numbers used to transfer TCP data segments from your client machine.

Dissecting FTP communication packets

There are two types of mode a client can use to communicate with a server: active and passive. In earlier versions...