Computer Communication

Requirements for using FTP

- An FTP client like Auto FTP manager installed on your computer - Certain information about FTP server: - The FTP server address - A user name and password. Some FTP servers let you connect to them anonymously.

What ports are used for the service?

Executing an FTP port connection through a client is a two-stage process requiring the use of two different ports. Once the user enters the name of the server and the login credentials in the authorization fields of the FTP client, the FTP connection is established and the FTP control port of the FTP server ( the default port for sending commands is 21 ) is opened. Then a second connection to the server is made by the client, followed by a response of the FTP server from the port for sending data ( the default data sending port is 20)

FTP and Internet Connections

FTP uses one connection for commands and the other for sending and receiving data. FTP has a standard port number on which the FTP server "listens" for connections. A port is a "logical connection point" for communicating using the internet protocol ( IP). The standard port number used by FTP servers is 21 and is used only for sending commands. Since port 21 is used exclusively for sending commands, this port is referred to as a command port. The port that is used for transferring data is referred to as a data port. The number of the data port will vary depending on the "mode" of the connection.

Investigate and explain how sockets are used for ftp?

FTP- File Transfer Protocol. Sockets are used to listen for connection requests and data transfers in FTP. Server just waits, listening to the socket for a client to make a connection request passively (Passive FTP) or actively (Active FTP).

What functionality is associated with each of these ports?

Port 21 is referred as a command port. Command port is used exclusively for sending commands. Active FTP servers generally use port 20 as their data port.

Sockets

Socket is an endpoint for communication. A pair of processes communicating over a network employs a pair of sockets- one for each process. A socket is identified by an IP address concatenated with a port number. A port is a "logical connection point" for communicating using the Internet Protocol.

Active and Passive connection mode

The FRP server may support Active or Passive connections or both.

Active FTP connection

The client opens a port and listens and the server actively connects to it.

What is FTP?

The file transfer protocol is used to transfer files between two computers over a network and internet. It also works between computers using totally different operating systems. Auto FTP manager is an advanced FTP client that automates files transfers between your computer and the FTP server.

Passive FTP connection

The server opens a port and listens passively and the client connects to it. Using passive mode, the FTP client is "reaching out" to the server to make the connection.