TELNET is a client/server application that allows a user to log on to a remote machine, giving the user access to the remote system.
TELNET uses the network virtual terminal (NVT) system to encode characters on the local system. On the server machine, NVT decodes the characters to a form acceptable to the remote machine.
NVT uses a set of characters for data and a set of characters for control.
In TELNET, control characters are embedded in the data stream and preceded by the interpret as control (lAC) control character.
Options are features that enhance the TELNET process.
TELNET allows negotiation to set transfer conditions between the client and server before and during the use of the service.
A TELNET implementation operates in the default, character, or line mode. 1. In the default mode, the client sends one line at a time to the server. 2. In the character mode, the client sends one character at a time to the server. 3. In the line mode, the client sends one line at a time to the server.
Several programs, including SMTP, POP3, and IMAP4, are used in the Internet to provide electronic mail services.
In electronic mail, the VA prepares the message, creates the envelope, and puts the message in the envelope.
In electronic mail, the mail address consists of two parts: a local part (user mailbox) and a domain name. The form is localpart@domainname.
In electronic mail, Multipurpose Internet Mail Extension (MIME) allows the transfer of multimedia messages.
In electronic mail, the MTA transfers the mail across the Internet, a LAN, or a WAN.
SMTP uses commands and responses to transfer messages between an MTA client and an MTA server.
The steps in transferring a mail message are 1. Connection establishment· 2. Mail transfer 3. Connection termination
Post Office Protocol, version 3 (POP3) and Internet Mail Access Protocol, version 4 (IMAP4) are protocols used for pulling messages from a mail server.
One of the programs used for file transfer in the Internet is File Transfer Protocol (FTP).
FTP requires two connections for data transfer: a control connection and a data connection.
FTP employs NVT ASCII for communication between dissimilar systems.
Prior to the actual transfer of files, the file type, data structure, and transmission mode are defined by the client through the control connection.
Responses are sent from the server to the client during connection establishment.
There are three types of file transfer: 1. A file is copied from the server to the client. 2. A file is copied from the client to the server. 3. A list of directories or file names is sent from the server to the client.
Anonymous FTP provides a method for the general public to access files on remote sites.
