Data Port (PORT) - KB Article #1451Related Articles --
The PORT command is issued by the client to initiate a data connection required to transfer data (such as directory listings or files) between the client and server. The PORT command is used during "active" mode transfers.
When issuing the PORT command, the client will include information on the address and port that the server is to use in order to connect back to the client. Thus, the structure of the PORT command is clearly defined to allow servers to parse this information from the command. The structure of the PORT command is: PORT (h1,h2,h3,h4,p1,p2).
The numbers used for the values of h1-h4 constitute the IP address the server should connect on. The numbers used for the values of p1-p2 are used to calculate the port number. In order to get the decimal value of the port, the following formula is used: (p1 * 256) + p2 = data port.