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$\textsf{HELO}$ and $\textsf{PORT}$, respectively, are commands from the protocols:

  1. $\textsf{FTP}$ and $\textsf{HTTP}$
  2. $\textsf{TELNET}$ and $\textsf{POP3}$
  3. $\textsf{HTTP}$ and $\textsf{TELNET}$
  4. $\textsf{SMTP}$ and $\textsf{FTP}$
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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

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