A Protocol Used for Uploading and Downloading Files Is

Standard protocol for transferring files over TCP/IP networks

File Transfer Protocol

Communication protocol
Purpose	File transfer
Developer(southward)	Abhay Bhushan for RFC 959
Introduction	April sixteen, 1971; l years ago  (1971-04-16)
OSI layer	Application layer
Port(s)	21 for command, twenty for data transfer
RFC(s)	RFC 959

The File Transfer Protocol (FTP) is a standard advice protocol used for the transfer of figurer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate command and data connections between the client and the server.^[1] FTP users may authenticate themselves with a clear-text sign-in protocol, unremarkably in the grade of a username and password, but tin connect anonymously if the server is configured to allow it. For secure transmission that protects the username and countersign, and encrypts the content, FTP is oftentimes secured with SSL/TLS (FTPS) or replaced with SSH File Transfer Protocol (SFTP).

The outset FTP client applications were command-line programs developed before operating systems had graphical user interfaces, and are nonetheless shipped with most Windows, Unix, and Linux operating systems.^{[2] [three]} Many FTP clients and automation utilities accept since been developed for desktops, servers, mobile devices, and hardware, and FTP has been incorporated into productivity applications, such as HTML editors.

In Jan 2021, support for the FTP protocol was disabled in Google Chrome 88,^[4] and disabled in Firefox 88.0.^[5] In July 2021, Firefox 90 dropped FTP entirely,^[six] and Google followed suit in October 2021, removing FTP entirely in Google Chrome 95.^[7]

History of FTP servers [edit]

The original specification for the File Transfer Protocol was written by Abhay Bhushan and published as RFC 114 on xvi April 1971. Until 1980, FTP ran on NCP, the predecessor of TCP/IP.^[2] The protocol was later replaced by a TCP/IP version, RFC 765 (June 1980) and RFC 959 (October 1985), the electric current specification. Several proposed standards amend RFC 959, for example RFC 1579 (February 1994) enables Firewall-Friendly FTP (passive mode), RFC 2228 (June 1997) proposes security extensions, RFC 2428 (September 1998) adds support for IPv6 and defines a new type of passive mode.^[8]

Protocol overview [edit]

Advice and information transfer [edit]

Analogy of starting a passive connectedness using port 21

FTP may run in agile or passive way, which determines how the data connexion is established.^[9] (This sense of "style" is different from that of the MODE command in the FTP protocol, and corresponds to the PORT/PASV/EPSV/etc commands instead.) In both cases, the customer creates a TCP control connectedness from a random, normally an unprivileged, port Northward to the FTP server command port 21.

• In active fashion, the client starts listening for incoming data connections from the server on port M. It sends the FTP command PORT Yard to inform the server on which port it is listening. The server then initiates a information channel to the client from its port 20, the FTP server data port.
• In situations where the client is behind a firewall and unable to accept incoming TCP connections, passive mode may be used. In this mode, the client uses the control connection to send a PASV command to the server and then receives a server IP address and server port number from the server,^[nine] which the client so uses to open a data connexion from an arbitrary client port to the server IP address and server port number received.^[ten]

Both modes were updated in September 1998 to back up IPv6. Further changes were introduced to the passive mode at that fourth dimension, updating it to extended passive style.^[xi]

The server responds over the control connection with iii-digit status codes in ASCII with an optional text message. For example, "200" (or "200 OK") ways that the terminal control was successful. The numbers correspond the lawmaking for the response and the optional text represents a human being-readable caption or request (eastward.grand. <Need account for storing file>).^[i] An ongoing transfer of file data over the information connection can be aborted using an interrupt bulletin sent over the control connection.

FTP needs two ports (i for sending and one for receiving) because it was originally designed to operate on Network Command Plan (NCP), which was a simplex protocol that utilized two port addresses, establishing two connections, for 2-way communications. An odd and an fifty-fifty port were reserved for each awarding layer application or protocol. The standardization of TCP and UDP reduced the need for the use of ii simplex ports for each application down to one duplex port,^{[12] : 15} but the FTP protocol was never contradistinct to merely use one port, and continued using two for backwards compatibility.

NAT and firewall traversal [edit]

FTP ordinarily transfers data past having the server connect dorsum to the customer, after the PORT control is sent by the client. This is problematic for both NATs and firewalls, which do not let connections from the Cyberspace towards internal hosts.^[13] For NATs, an additional complication is that the representation of the IP addresses and port number in the PORT command refer to the internal host's IP address and port, rather than the public IP accost and port of the NAT.

There are two approaches to solve this problem. I is that the FTP customer and FTP server use the PASV command, which causes the data connection to exist established from the FTP client to the server.^[13] This is widely used by modern FTP clients. Another approach is for the NAT to alter the values of the PORT control, using an awarding-level gateway for this purpose.^[13]

Data types [edit]

While transferring data over the network, four data types are defined:^{[ii] [3] [8]}

• ASCII (TYPE A): Used for text. Data is converted, if needed, from the sending host's grapheme representation to "8-bit ASCII" before transmission, and (again, if necessary) to the receiving host'south character representation. As a consequence, this manner is inappropriate for files that contain data other than plain text.
• Prototype (TYPE I, normally called Binary mode): The sending machine sends each file byte by byte, and the recipient stores the bytestream as it receives it. (Paradigm mode support has been recommended for all implementations of FTP).
• EBCDIC (Type E): Used for patently text betwixt hosts using the EBCDIC character gear up.
• Local (TYPE L due north): Designed to support file transfer between machines which do not utilise eight-bit bytes, e.g. 36-scrap systems such as Dec PDP-10s. For example, "Blazon Fifty ix" would be used to transfer information in nine-bit bytes, or "TYPE 50 36" to transfer 36-bit words. Most contemporary FTP clients/servers only back up Fifty eight, which is equivalent to I.

An expired Cyberspace Draft divers a TYPE U for transferring Unicode text files using UTF-8;^[14] although the draft never became an RFC, information technology has been implemented by several FTP clients/servers.

Note these information types are commonly called "modes", although ambiguously that word is also used to refer to agile-vs-passive communication mode (see above), and the modes set by the FTP protocol MODE command (see below).

For text files (Blazon A and TYPE E), three different format command options are provided, to command how the file would be printed:

• Not-impress (TYPE A North and TYPE Due east North) – the file does not contain any wagon control characters intended for a printer
• Telnet (TYPE A T and Blazon E T) – the file contains Telnet (or in other words, ASCII C0) carriage control characters (CR, LF, etc)
• ASA (Type A A and Blazon E A) – the file contains ASA carriage control characters

These formats were mainly relevant to line printers; most contemporary FTP clients/servers just support the default format control of Northward.

File structures [edit]

File system is specified using the STRU command. The following file structures are defined in section 3.1.i of RFC959:

• F or FILE structure (stream-oriented). Files are viewed as an arbitrary sequence of bytes, characters or words. This is the usual file structure on Unix systems and other systems such every bit CP/K, MS-DOS and Microsoft Windows. (Section 3.i.one.1)
• R or RECORD structure (record-oriented). Files are viewed as divided into records, which may be fixed or variable length. This file organization is common on mainframe and midrange systems, such as MVS, VM/CMS, Bone/400 and VMS, which support tape-oriented filesystems.
• P or PAGE structure (page-oriented). Files are divided into pages, which may either contain data or metadata; each page may besides have a header giving various attributes. This file structure was specifically designed for TENEX systems, and is generally not supported on other platforms. RFC1123 section 4.1.2.3 recommends that this structure non be implemented.

Well-nigh contemporary FTP clients and servers just support STRU F. STRU R is yet in use in mainframe and minicomputer file transfer applications.

Information transfer modes [edit]

Data transfer can be done in any of three modes:^{[1] [2]}

• Stream style (Style South): Information is sent as a continuous stream, relieving FTP from doing any processing. Rather, all processing is left up to TCP. No Terminate-of-file indicator is needed, unless the data is divided into records.
• Block fashion (Way B): Designed primarily for transferring record-oriented files (STRU R), although can also be used to transfer stream-oriented (STRU F) text files. FTP puts each record (or line) of data into several blocks (block header, byte count, and data field) and so passes it on to TCP.^[viii]
• Compressed mode (Style C): Extends Fashion B with data compression using run-length encoding.

Most gimmicky FTP clients and servers practice not implement Fashion B or Mode C; FTP clients and servers for mainframe and minicomputer operating systems are the exception to that.

Some FTP software also implements a Debunk-based compressed way, sometimes called "Manner Z" after the command that enables it. This fashion was described in an Internet Draft, but not standardized.^[15]

GridFTP defines additional modes, Mode E^[16] and Fashion Ten,^[17] equally extensions of Fashion B.

Additional commands [edit]

More than contempo implementations of FTP back up the Modify Fact: Modification Time (MFMT) control, which allows a client to accommodate that file attribute remotely, enabling the preservation of that attribute when uploading files.^{[18] [nineteen]}

To retrieve a remote file timestamp, at that place's MDTM command. Some servers (and clients) support nonstandard syntax of the MDTM command with 2 arguments, that works the same style equally MFMT ^[xx]

Login [edit]

FTP login uses normal username and countersign scheme for granting admission.^[2] The username is sent to the server using the USER command, and the password is sent using the PASS command.^[two] This sequence is unencrypted "on the wire", so may exist vulnerable to a network sniffing attack.^[21] If the information provided by the client is accustomed by the server, the server will send a greeting to the client and the session will embark.^[2] If the server supports it, users may log in without providing login credentials, but the same server may authorize merely limited admission for such sessions.^[2]

Anonymous FTP [edit]

A host that provides an FTP service may provide anonymous FTP admission.^[2] Users typically log into the service with an 'bearding' (lower-case and case-sensitive in some FTP servers) account when prompted for user name. Although users are commonly asked to transport their e-mail address instead of a countersign,^[3] no verification is really performed on the supplied data.^[22] Many FTP hosts whose purpose is to provide software updates will permit anonymous logins.^[three]

Differences from HTTP [edit]

HTTP essentially fixes the bugs in FTP that made it inconvenient to use for many small ephemeral transfers equally are typical in web pages.

FTP has a stateful command connection which maintains a current working directory and other flags, and each transfer requires a secondary connection through which the data are transferred. In "passive" mode this secondary connectedness is from customer to server, whereas in the default "active" mode this connection is from server to client. This apparent office reversal when in agile fashion, and random port numbers for all transfers, is why firewalls and NAT gateways have such a hard fourth dimension with FTP. HTTP is stateless and multiplexes control and data over a unmarried connection from customer to server on well-known port numbers, which trivially passes through NAT gateways and is simple for firewalls to manage.

Setting upwardly an FTP control connection is quite slow due to the round-trip delays of sending all of the required commands and awaiting responses, then it is customary to bring upward a control connection and hold information technology open up for multiple file transfers rather than drop and re-establish the session afresh each time. In dissimilarity, HTTP originally dropped the connectedness after each transfer because doing then was and so cheap. While HTTP has subsequently gained the ability to reuse the TCP connection for multiple transfers, the conceptual model is yet of independent requests rather than a session.

When FTP is transferring over the data connection, the command connection is idle. If the transfer takes likewise long, the firewall or NAT may decide that the control connection is expressionless and end tracking it, effectively breaking the connexion and confusing the download. The single HTTP connectedness is only idle between requests and it is normal and expected for such connections to be dropped after a time-out.

Software support [edit]

Spider web browser [edit]

Virtually common web browsers can retrieve files hosted on FTP servers, although they may not support protocol extensions such every bit FTPS.^{[3] [23]} When an FTP—rather than an HTTP—URL is supplied, the accessible contents on the remote server are presented in a manner that is similar to that used for other spider web content. FireFTP is an browser extension designed as a full-featured FTP customer, it could exist run inside Firefox in the past, but it's now recommend working with Waterfox.

Google Chrome removed FTP support entirely in Chrome 88.^[24] Equally of 2019, Mozilla was discussing proposals, including only removing support for erstwhile FTP implementations that are no longer in use to simplify their code.^{[25] [26]} In Apr, 2021, Mozilla released Firefox 88.0 which disabled FTP support by default.^[27] In July 2021, Firefox 90 dropped FTP back up entirely.^[vi]

Syntax [edit]

FTP URL syntax is described in RFC 1738, taking the form: ftp://[user[:password]@]host[:port]/url-path (the bracketed parts are optional).

For example, the URL ftp://public.ftp-servers.example.com/mydirectory/myfile.txt represents the file myfile.txt from the directory mydirectory on the server public.ftp-servers.example.com as an FTP resource. The URL ftp://user001:secretpassword@individual.ftp-servers.example.com/mydirectory/myfile.txt adds a specification of the username and countersign that must be used to admission this resource.

More than details on specifying a username and password may exist institute in the browsers' documentation (due east.g., Firefox^[28] and Internet Explorer^[29]). By default, virtually web browsers utilise passive (PASV) mode, which more hands traverses end-user firewalls.

Some variation has existed in how different browsers treat path resolution in cases where there is a not-root home directory for a user.^[30]

Download manager [edit]

Most common download managers can receive files hosted on FTP servers, while some of them besides requite the interface to retrieve the files hosted on FTP servers. DownloadStudio and Internet Download Accelerator allows not only download a file from FTP server but also view the listing of files on a FTP server.^{[31] [32]}

Security [edit]

FTP was not designed to exist a secure protocol, and has many security weaknesses.^[33] In May 1999, the authors of RFC 2577 listed a vulnerability to the following problems:

• Brute-force attack
• FTP bounciness assail
• Packet capture
• Port stealing (guessing the adjacent open port and usurping a legitimate connection)
• Spoofing set on
• Username enumeration
• DoS or DDoS

FTP does not encrypt its traffic; all transmissions are in clear text, and usernames, passwords, commands and information can be read by anyone able to perform packet capture (sniffing) on the network.^{[2] [33]} This problem is common to many of the Internet Protocol specifications (such as SMTP, Telnet, Pop and IMAP) that were designed prior to the creation of encryption mechanisms such as TLS or SSL.^[viii]

Common solutions to this problem include:

1. Using the secure versions of the insecure protocols, e.g., FTPS instead of FTP and TelnetS instead of Telnet.
2. Using a dissimilar, more secure protocol that can handle the job, eastward.g. SSH File Transfer Protocol or Secure Copy Protocol.
3. Using a secure tunnel such as Secure Shell (SSH) or virtual private network (VPN).

FTP over SSH [edit]

FTP over SSH is the do of tunneling a normal FTP session over a Secure Shell connection.^[33] Considering FTP uses multiple TCP connections (unusual for a TCP/IP protocol that is still in use), information technology is specially difficult to tunnel over SSH. With many SSH clients, attempting to set a tunnel for the command channel (the initial client-to-server connection on port 21) will protect only that channel; when data is transferred, the FTP software at either end sets up new TCP connections (data channels) and thus accept no confidentiality or integrity protection.

Otherwise, it is necessary for the SSH customer software to accept specific knowledge of the FTP protocol, to monitor and rewrite FTP control channel messages and autonomously open new packet forwardings for FTP information channels. Software packages that support this mode include:

• Tectia ConnectSecure (Win/Linux/Unix)^[34] of SSH Communications Security's software suite

Derivatives [edit]

FTPS [edit]

Main article: FTPS

Explicit FTPS is an extension to the FTP standard that allows clients to request FTP sessions to exist encrypted. This is done by sending the "AUTH TLS" command. The server has the option of allowing or denying connections that do not asking TLS. This protocol extension is divers in RFC 4217. Implicit FTPS is an outdated standard for FTP that required the utilize of a SSL or TLS connection. It was specified to utilize different ports than plain FTP.

SSH File Transfer Protocol [edit]

The SSH file transfer protocol (chronologically the 2d of the two protocols abbreviated SFTP) transfers files and has a similar command gear up for users, but uses the Secure Trounce protocol (SSH) to transfer files. Dissimilar FTP, it encrypts both commands and data, preventing passwords and sensitive information from beingness transmitted openly over the network. It cannot interoperate with FTP software.

Lilliputian File Transfer Protocol [edit]

Trivial File Transfer Protocol (TFTP) is a elementary, lock-step FTP that allows a client to get a file from or put a file onto a remote host. One of its master uses is in the early on stages of booting from a local expanse network, because TFTP is very simple to implement. TFTP lacks security and most of the advanced features offered past more robust file transfer protocols such as File Transfer Protocol. TFTP was first standardized in 1981 and the current specification for the protocol tin can be institute in RFC 1350.

Simple File Transfer Protocol [edit]

Simple File Transfer Protocol (the first protocol abbreviated SFTP), every bit defined by RFC 913, was proposed every bit an (unsecured) file transfer protocol with a level of complication intermediate between TFTP and FTP. Information technology was never widely accepted on the Cyberspace, and is now assigned Historic condition by the IETF. It runs through port 115, and oft receives the initialism of SFTP. It has a command fix of 11 commands and support three types of data transmission: ASCII, binary and continuous. For systems with a word size that is a multiple of eight $.25, the implementation of binary and continuous is the same. The protocol also supports login with user ID and countersign, hierarchical folders and file direction (including rename, delete, upload, download, download with overwrite, and download with append).

FTP commands [edit]

FTP reply codes [edit]

Below is a summary of FTP reply codes that may be returned by an FTP server. These codes have been standardized in RFC 959 past the IETF. The answer code is a three-digit value. The starting time digit is used to bespeak one of iii possible outcomes — success, failure, or to indicate an fault or incomplete respond:

• 2yz – Success reply
• 4yz or 5yz – Failure reply
• 1yz or 3yz – Error or Incomplete answer

The second digit defines the kind of error:

• x0z – Syntax. These replies refer to syntax errors.
• x1z – Data. Replies to requests for information.
• x2z – Connections. Replies referring to the command and data connections.
• x3z – Hallmark and accounting. Replies for the login procedure and bookkeeping procedures.
• x4z – Not defined.
• x5z – File organisation. These replies relay status codes from the server file system.

The third digit of the reply code is used to provide additional particular for each of the categories defined by the second digit.

See likewise [edit]

• Comparison of FTP client software
• Comparison of FTP server software packages
• Comparing of file transfer protocols
• Coil-loader – FTP/Due south loading/testing open-source software
• File commutation Protocol (FXP)
• File Service Protocol (FSP)
• FTAM
• FTPFS
• Listing of FTP commands
• List of FTP server return codes
• Managed File Transfer
• OBEX
• Shared file access
• TCP Wrapper

References [edit]

1. ^ ^{a b c} Forouzan, B.A. (2000). TCP/IP: Protocol Suite (1st ed.). New Delhi, India: Tata McGraw-Hill Publishing Visitor Express.
2. ^ ^{a b c d e f g h i j} Kozierok, Charles One thousand. (2005). "The TCP/IP Guide v3.0". Tcpipguide.com.
3. ^ ^{a b c d due east} Dean, Tamara (2010). Network+ Guide to Networks. Delmar. pp. 168–171.
4. ^ "Deprecations and removals in Chrome 87". Retrieved 18 November 2020.
5. ^ "Firefox 88.0, Come across All New Features, Updates and Fixes". Retrieved 23 Apr 2021.
6. ^ ^{a b} Vonau, Manuel (7 July 2021). "Firefox follows in Chrome's footsteps and drops FTP support (APK Download)". Android Police . Retrieved 12 July 2021. {{cite web}}: CS1 maint: url-status (link)
7. ^ "Remove FTP support - Chrome Platform Condition". www.chromestatus.com . Retrieved 2 September 2021.
8. ^ ^{a b c d} Clark, M.P. (2003). Data Networks IP and the Internet (1st ed.). West Sussex, England: John Wiley & Sons Ltd.
9. ^ ^{a b} "Active FTP vs. Passive FTP, a Definitive Explanation". Slacksite.com.
10. ^ RFC 959 (Standard) File Transfer Protocol (FTP). Postel, J. & Reynolds, J. (Oct 1985).
11. ^ RFC 2428 (Proposed Standard) Extensions for IPv6, NAT, and Extended Passive Mode. Allman, Yard. & Metz, C. & Ostermann, S. (September 1998).
12. ^ Stevens, Due west. Richard (1994). TCP/IP Illustrated Volume I. Vol. i. Reading, Massachusetts, Us: Addison-Wesley Publishing Company. ISBN0-201-63346-9.
13. ^ ^{a b c} Gleason, Mike (2005). "The File Transfer Protocol and Your Firewall/NAT". Ncftp.com.
14. ^ Klensin, John. FTP TYPE Extension for Internationalized Text. I-D draft-klensin-ftpext-typeu-00. Retrieved 9 June 2020.
15. ^ Preston, J. (January 2005). Deflate manual fashion for FTP. IETF. I-D draft-preston-ftpext-deflate-03. Retrieved 27 January 2016.
16. ^ Allcock, W. (April 2003). "GridFTP: Protocol Extensions to FTP for the Filigree" (PDF).
17. ^ Mandrichenko, I. (4 May 2005). "GridFTP v2 Protocol Clarification" (PDF).
18. ^ "MFMT FTP command". back up.solarwinds.com. 11 October 2018.
19. ^ "FTP Commands: DSIZ, MFCT, MFMT, AVBL, PASS, XPWD, XMKD | Serv-U". www.serv-u.com.
20. ^ "MDTM FTP control". support.solarwinds.com. 11 October 2018.
21. ^ Prince, Brian. "Should Organizations Retire FTP for Security?". Security Week. Security Week. Retrieved xiv September 2017.
22. ^ RFC 1635 (Informational) How to Employ Anonymous FTP. P. & Emtage, A. & Marine, A. (May 1994).
23. ^ Matthews, J. (2005). Computer Networking: Internet Protocols in Action (1st ed.). Danvers, MA: John Wiley & Sons Inc.
24. ^ Sneddon, Joey (26 January 2021). "Linux Release Roundup: GParted, Lightworks, Google Chrome + More". omgubuntu.co.u.k. . Retrieved xxx January 2021.
25. ^ "1574475 - Remove FTP support".
26. ^ "Deprecate FTP back up - Chrome Platform Status".
27. ^ "See what'southward new in Firefox: 88.0 Firefox Release". mozilla.org. nineteen April 2021. Retrieved 20 April 2021.
28. ^ "Accessing FTP servers | How to | Firefox Assist". Support.mozilla.com. 5 September 2012. Retrieved 16 Jan 2013.
29. ^ "How to Enter FTP Site Password in Cyberspace Explorer". Archived from the original on 2 July 2015. Retrieved 13 Feb 2020. {{cite web}}: CS1 maint: bot: original URL status unknown (link) Written for IE versions 6 and earlier. Might piece of work with newer versions.
30. ^ Jukka "Yucca" Korpela (18 September 1997). "FTP URLs". "It and communication" (jkorpela.fi). Retrieved 26 January 2020.
31. ^ "DownloadStudio - Net Download Manager And Download Accelerator - Features". Conceiva. Retrieved nineteen October 2021.
32. ^ "Net Download Accelerator | Features". WestByte. Retrieved xx Oct 2021.
33. ^ ^{a b c} "Securing FTP using SSH". Nurdletech.com.
34. ^ "Components of the Information Balls Platform (department Tectia ConnectSecure)". ssh.com. Archived from the original on 31 July 2020.

Farther reading [edit]

• RFC 697 – CWD Control of FTP. July 1975.
• RFC 959 – (Standard) File Transfer Protocol (FTP). J. Postel, J. Reynolds. Oct 1985.
• RFC 1579 – (Advisory) Firewall-Friendly FTP. Feb 1994.
• RFC 1635 – (Advisory) How to Use Bearding FTP. May 1994.
• RFC 1639 – FTP Operation Over Large Address Records (FOOBAR). June 1994.
• RFC 1738 – Uniform Resource Locators (URL). December 1994.
• RFC 2228 – (Proposed Standard) FTP Security Extensions. October 1997.
• RFC 2389 – (Proposed Standard) Feature negotiation mechanism for the File Transfer Protocol. Baronial 1998.
• RFC 2428 – (Proposed Standard) Extensions for IPv6, NAT, and Extended passive mode. September 1998.
• RFC 2577 – (Informational) FTP Security Considerations. May 1999.
• RFC 2640 – (Proposed Standard) Internationalization of the File Transfer Protocol. July 1999.
• RFC 3659 – (Proposed Standard) Extensions to FTP. P. Hethmon. March 2007.
• RFC 5797 – (Proposed Standard) FTP Command and Extension Registry. March 2010.
• RFC 7151 – (Proposed Standard) File Transfer Protocol HOST Command for Virtual Hosts. March 2014.
• IANA FTP Commands and Extensions registry – The official registry of FTP Commands and Extensions

External links [edit]

• Communication Networks/File Transfer Protocol at Wikibooks
• FTP Server Online Tester Authentication, encryption, mode and connectivity.
• Anonymous FTP Servers by Country Code TLD (2012): "Offbeat Net - Public Admission - FTP". www.jumpjet.info. 2012. Retrieved 16 January 2020.

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Source: https://en.wikipedia.org/wiki/File_Transfer_Protocol

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