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+15 votes
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HELO and PORT, respectively, are commands from the protocols:

  1. FTP and HTTP
  2. TELNET and POP3
  3. HTTP and TELNET
  4. SMTP and FTP
asked in Computer Networks by Boss (19.1k points)
edited by | 1.5k views
+4
HELO - Sender's Host Name (SMTP)
PORT -  is a ftp command.

6 Answers

+13 votes
+17 votes

answer is D

HELO:  The domain name or IP address of the SMTP client is usually sent as an argument together with the command (e.g. “HELO client.example.com”). If a domain name is used as an argument with the HELO command, it must be a fully qualified domain name (also called FQDN).

FTP  : FTP may run in active or passive mode, which determines how the data connection is established. In both cases, the client creates a TCP control connection from a random, usually an unprivileged, port N to the FTP server command port 21.

answered by Active (2.7k points)
+10 votes

For SMTP: Various commands

  1. HELO : It's the first SMTP command: is starts the conversation identifying the sender server and is generally followed by its domain name.
  2. EHLO : An alternative command to start the conversation, underlying that the server is using the Extended SMTP protocol.
  3. MAIL FROM : With this SMTP command the operations begin: the sender states the source email address in the "From" field and actually starts the email transfer.
  4. RCPT TO : It identifies the recipient of the email; if there are more than one, the command is simply repeated address by address.
  5. SIZE : This SMTP command informs the remote server about the estimated size (in terms of bytes) of the attached email. It can also be used to report the maximum size of a message to be accepted by the server.
  6. DATA : With the DATA command the email content begins to be transferred; it's generally followed by a 354 reply code given by the server, giving the permission to start the actual transmission.
  7. VRFY : The server is asked to verify whether a particular email address or username actually exists.
  8. TURN: This command is used to invert roles between the client and the server, without the need to run a new connaction.
  9. AUTH : With the AUTH command, the client authenticates itself to the server, giving its username and password. It's another layer of security to guarantee a proper transmission.
  10. RSET : It communicates the server that the ongoing email transmission is going to be terminated, though the SMTP conversation won't be closed (like in the case of QUIT).
  11. EXPN : This SMTP command asks for a confirmation about the identification of a mailing list.
  12. HELP : It's a client's request for some information that can be useful for the a successful transfer of the email.
  13. QUIT : It terminates the SMTP conversation.

FTP may run in active or passive mode, which determines how the data connection is established. In both cases, the client creates a TCP control connection from a random, usually an unprivileged, port N to the FTP server command port 21.

For HTTP commands :

  1. GET :Retrieves the document specified in the URL property (use GetHeader to retrieve header information and GetChunk to get the rest of the information)
  2. HEAD: Gets the header information (use Get Header to retrieve header information).
  3. POST : Sends data to the server.
  4. PUT : Replaces the page specified in the URL property with the specified data

D is answer

answered by Boss (17.8k points)
0
Where did u get this ?? resources ??
0
From book Forouzan .
0
FTP has port number 21 too
+1 vote
ans d)
answered by Loyal (5.3k points)
+1 vote
Option-D

HELO(HELLO) and Port is usualy command of SMTP as well as FTP.

For more information please read the book of Top down approach of computer network.
answered by Loyal (9.1k points)
0 votes

FTP uses 2 port number values -- one for commands (port 21 by default), and one for data transfer(can be any). 

The PORT command is sent by an FTP client to establish a secondary connection (address and port) for data to travel over. In some FTP implementations port 20 is used for data, but that is the exception rather than the rules

answered by Junior (985 points)
Answer:

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