TCP/IP provides a total of 65,535 ports of which 1023 are considered to be ''well known'' ports. In reality the number of ports that are used by popular network clients and services comprises an even smaller subset of the well known group of ports. The following table lists the functions of this subset.

TCP/IP provides a total of 65,535 ports of which 1023 are considered to be ''well known'' ports. In reality the number of ports that are used by popular network clients and services comprises an even smaller subset of the well known group of ports. The following table lists the functions of this subset.

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<td>'''20'''</td><td>'''FTP'''<td>'''File Transfer Protocol (Data)''' - The File Transfer protocol provides a mechanism for transferring specific files between network connected computer systems (usually a Linux or UNIX based system). Transfer is typically performed using the ''ftp'' client which provides a range of commands used to connect to a remote server for the purpose of uploading or downloading files. Most modern web browsers also have the ability to browse and download files located on a remote FTP server. FTP uses TCP (rather than UDP) to transfer files so is considered to be a highly reliable tranport mechanism.</td>

<td>'''20'''</td><td>'''FTP'''<td>'''File Transfer Protocol (Data)''' - The File Transfer protocol provides a mechanism for transferring specific files between network connected computer systems (usually a Linux or UNIX based system). Transfer is typically performed using the ''ftp'' client which provides a range of commands used to connect to a remote server for the purpose of uploading or downloading files. Most modern web browsers also have the ability to browse and download files located on a remote FTP server. FTP uses TCP (rather than UDP) to transfer files so is considered to be a highly reliable transport mechanism. FTP does not encrypt data and is not considered to be a secure file transfer protocol. The use of Secure Copy Protocol (''SCP'') and Secure File Transfer Protocol (''SFTP'') is strongly recommended in place of FTP.</td>

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