FTP protocol (SFTP, FTPS) - what is it, connection between client and server via FTP.

Hello, dear readers of the blog site. The next step on the path to understanding the mechanism of information transfer on the Internet will be to study FTP, through which you can, among other things, work with any files on a remote server.

.jpg

Or apply more difficult option, if a port other than 21 is used:

Ftp://login:password@site:35/images/file-1.jpg

However, using a web browser in this context will only allow you to view or download the files of interest. To take full advantage of all the benefits of FTP, you should use specialized software like Filezilla():

To connect through an already configured FileZilla client to a remote server, you must enter the name of the host, which is used, corresponding to its domain ( and ), username, password and port.

By the way, in the article about Filezilla it is given not only standard information, but also practical advice to eliminate its security vulnerabilities (despite a bunch of advantages, it has problems of this kind, however, like other programs of a similar profile), so I strongly recommend reading this material by clicking on the link provided just above.

But let's continue. Schematically, the client-server interaction during an FTP connection can be visualized as follows:

If we describe this process point by point, it will look something like this:

1. User activates client application and connects to the server by entering your login and password.
2. Installed control connection between the corresponding modules - protocol interpreters on the client and server sides.
3. The user, through the client, sends commands to the server that determine various parameters FTP connections ( active or passive mode , port, type of data transfer, their type), as well as directives for actions that the user intends to carry out (for example, delete, rename, upload a file, etc.).
4. After all the necessary parameters have been set, one of the participants (for example, a client), which is passive, becomes in the waiting mode for opening a connection to the port that is specified for transmitting information. The active participant then opens a connection and begins transmitting data over the designated channel.
5. Upon completion of the transfer, this connection is closed, but the control channel between the interpreters remains open, as a result of which the user can reopen the data transfer within the same session.

If the user is the administrator of a site that is located on a remote server, then after authentication and connection he is able to perform any possible actions.

However, there are quite a lot of free FTP servers on the Internet, which are essentially libraries of various kinds of files that are intended for storage and downloading text documents, music, photos, videos, software distributions, etc.

In this case, the registered user, after authorization, has a very limited access to certain directories and can only perform certain specified operations with their contents (for example, viewing and downloading files).

In addition to the standard connection to the server, which requires entering authentication data, there is concept of anonymous FTP, when any user can connect to the server without providing personal data. If you use a browser as a client, the file access address can be simplified and presented like this:

Ftp://site/images/file-1.jpg

In practice, with anonymous FTP, the word “anonymous”, known on the network, is usually used as a login for access, and the address is used as a password Email, which, however, is not checked in most cases.

Secure FTP (SFTP, FTPS and using SSH)

This protocol was not originally intended to be secure, as it was developed back in 1971 and was initially used only in the APRANET research network, to which only a few military facilities and universities had access.

But with the development of the World Wide Web, the aforementioned APRANET became part of it, and, consequently, FTP technology migrated there, since it had many advantages. However, at the same time, the risk of unauthorized access has increased by several orders of magnitude.

Therefore, there is an urgent need to protect servers from various types of attacks. A regular FTP does not have the ability to transmit data in encrypted form, as a result of which user names, passwords, commands and other information can be easily and easily intercepted by attackers.

For this reason, several methods have been developed to encrypt information transmitted via FTP. Together, all these methods received a general and capacious name "Secure FTP". Here are the types of protocol that correspond to this term:

1. FTPS(FTP + SSL) - in fact, this is an extension of the standard file transfer protocol, which is provided with cryptographic SSL protocol(Secure Sockets Layer - level of secure sockets). Today, its more advanced analogue is TLS (Transport Layer Security). There are two methods of providing security:

1.1. Implicit is obsolete and uses a standard protocol that requires SSL or TLS, which can provide encryption of information. With this method, it is necessary to use ports other than the usual ones, which creates inconvenience because it breaks the compatibility of clients and servers that do not support FTPS.

1.2. Explicit- much more convenient, since it uses standard commands FTP protocol, but encrypts the information when sending the response, which allows you to maintain compatibility, since in this case the same ports are used for both FTPS and FTP. In this case, the client sends the “AUTH TLS” or “AUTH SSL” command to encrypt the data.

2. SFTP(SSH FTP) - protocol application level for file transfer that runs on top of a secure channel, it should not be confused with "Simple File Transfer Protocol", which has the same abbreviation. If FTPS is simply an extension of FTP, then SFTP is a separate and in no way related to FTP protocol, which is equipped with SSH (Secure Shell).

The main thing that distinguishes it from standard FTP and FTPS is that SFTP encrypts absolutely all commands, usernames, passwords and other confidential information. Because this is a completely different configuration, FTP (FTPS) clients cannot connect to the SFTP server.

3. FTP over SSH— produces a regular FTP session through an SSH tunnel, that is, this option should not be confused with SFTP, which is a separate independent protocol. This method cannot be called 100% safe. Why?

The fact is that if several SSH clients establish a tunnel for a control channel, which is initially carried out through port 21 (and this situation is almost always observed), then this particular channel will be protected. When transferring data, the client software will open new TCP connections that will no longer be under the influence of the SSH protective shell.

I hope you are not confused by all these secure protocol options. In order to somehow facilitate understanding, let me make a brief summary. Objectively providing the most high degree security is SFTP. Explicit FTPS is slightly inferior in reliability, but it is more convenient because it allows you to use regular ports. Which one to choose depends on the type of task you are faced with and, of course, the server settings.

If you are the owner of a website, you have probably wondered how to access a website via ftp? The fact is that sites consist of files that are located on a remote server. These files can be accessed both through the hosting web panel and through ftp connection, which is much more convenient.

Before connecting to your site via ftp, you need to know the ftp server itself and the credentials that have access to connect to the server. Read on for more details...

To connect to the site via ftp I use FileZilla program. For today, this is the most convenient program for these purposes. Frequent updates programs eliminate the possibility of malicious connection to your site.

Download and install the program. After installation, run it

FileZilla is a convenient file manager, on the left side of which there is a panel with local files(on your computer), and on the right side you will see the files on the server (after connecting).

To connect to the server you need to know your credentials. Usually, the hoster sends them to the email address that was specified during registration. We find the letter and open it. This is what it looked like for me when I registered my first website

As you can see, there is the server itself, login, password. Now open FileZilla, click on the “Site Manager” button

In the window that opens, click “New site” and enter our data

After entering the data, click the “OK” button, the settings window will close. After this, click the arrow next to the “Site Manager” button and select “New site” (the one we just created)

If you entered all the data correctly, the program will connect you to the server, and a folder with files on the server will appear in the right window

Now, in order to copy a file to the site, or vice versa, pull a file from the site, you just need to go to the folder in right column select the desired directory and drag and drop the file into left column(in it also indicate the path to which you want to save the file).

When finished, simply close FileZilla. As you can see, there is nothing scary or incomprehensible. Everything is very easy and simple. If you still have questions, ask in the comments, I will be happy to help.

FTP is a protocol that is indispensable for website builders. Using the FTP data transfer protocol, the site can be loaded quickly necessary information. This protocol allows you to work with large amounts of information and does everything on high speed. Therefore, webmasters who decide to upload site data to hosting using the FTP protocol are making the right choice!

And although using FTP is easier than ever, most novice webmasters do not get familiar with the FTP server and client the first time. Therefore, in this article you will learn how you can upload your website to hosting via FTP, how to find out the FTP website address, and then connect to it and log into the server.

How to upload data to hosting via FTP

Your website hosting is an FTP server. To enter its file system and download the necessary distributions, you need a special client. Essentially this is regular program, which allows you to conveniently manipulate file system and work through different types data transfer protocols. The most popular client that can be downloaded for free is FileZilla. Most hosting providers recommend this particular program in their instructions for working with the server.

So, install FileZilla on your computer, or any other client. The installation will not take much time and is practically no different from a typical installation of programs in Windows. Next you need to open Top Menu“File” and select “Site Manager”. The next step is to add a new site to your FTP manager. In the host name field, enter the address of your site via FTP, in the “Login type” line, check “Request password”, and then in the “User” column fill in your login information: login and password.

You also need to configure the data transfer parameters. The fact is that the client works over two connections to the server. One connection is needed to send commands to the hosting, and the second so that you can load and unload data from the server. You need to select the mode for the data connection: active or passive.

And in passive mode, commands are issued by the server, not the client, which is more logical. In addition, sometimes the server does not display folders in active mode.

After defining the settings, you can try to log into the hosting - to do this, click the “Connect” button. Then a pop-up window will appear where you need to enter the password for your FTP server account. After connecting, two control panels will open in front of you in FileZilla. On one side there will be a panel for managing the computer’s file system, and on the other - the server. You need to find the WWW folder in the panel where the server manager is located. Your website domain will be placed inside it. Open it, immediately delete index.html and prepare to transfer data to the server from your computer. To do this, select the files on your PC in another control panel, and using right button mouse and find the “Upload to server” item.

Over time specified files will be uploaded to the hosting. It’s easy to find out about this - they will appear in the server control panel. Please note that you can use the FileZilla client not only as a tool for downloading data to a server or computer. Through it you can conveniently manage the file system: rename, edit, view, move, copy, delete or create files. FileZilla is much more functional than the standard one Windows Explorer, so you can perform many different operations and actions on the server.

How to determine the hostname for an FTP connection

Sometimes you can’t easily connect to a server because the host name to connect to is unknown. To log into the server, you will have to rummage a little through the hosting information in order to find out the name of the host. Otherwise, you will not be able to connect your computer to the hosting and download the necessary data for it.

As a rule, connection data can be found in the administration panel of the hosting. Please note that the information for logging into the admin panel of the hosting differs from the information for connecting to the server via FTP. If in personal account you didn't find any data, then go to Mailbox, which you specified when registering with the hosting provider. You should have received a message containing the host name, user name, and login password. If this is the case, then save this data somewhere else, and delete the letter itself from your computer so that no one else sees it.

Sometimes the anti-SPAM system recognizes a letter with login information for an FTP server as a viral mailing. In this case, check the folder where the SPAM is stored. If this idea does not help, then contact support. Usually, technical support Always responds quickly to problems encountered by hosting provider clients. After all, you pay money because you are potential profit for the hosting. Therefore, the attitude towards you will be affectionate, courteous, and the reaction to the problem that has arisen will be quick and adequate. You will soon be informed where your FTP server login information is stored. They will not send information directly because they do not have access to such data.

Is it possible to access an FTP server using standard Windows features?

It happens that there is no way to waste time downloading and installing any third-party applications to log into the server. In such situations, you can use standard features operating room Windows systems, which are enough to go to the server and upload site files there.

You need to open Explorer and any folder. Or you can open My Computer. At the top you will see the path to this directory. You need to erase it, and instead of this path, enter the login information for the FTP server via ftp://. Data must be specified in a clear sequence. First, you should specify the login to log into the server, then enter the password without spaces separated by a colon, then designate the dog @ and immediately, without spaces, enter the host name or its IP address for the connection.

After this is done, the FTP server will open directly on your computer in Explorer. That is, it will feel as if it is on your PC, and not on a remote hosting. By opening another folder with files, you can drag and drop the necessary data onto the server. They use special clients because the explorer is not very convenient to work with the server. Keeping two folders open unpinned is inconvenient compared to FileZIlla's well-thought-out interface.

You can also log into the server using the ftp://Server request (that is, the host name), but then you will need to enter your username and password to log in. As you can see, everything is very simple and there is nothing supernatural about FTP.

FTP (File Transfer Protocol) is one of the standard protocols, created for TCP/IP and approved in 1971. Used to download web pages from private devices to hosting servers.

What is FTP

Formally, FTP means connecting to specific folder, which is located on the server via the Internet. Despite its impressive age, this protocol is still used to transfer files, access remote hosts, and distribute software.

Unlike HTTP, FTP is session-based, supports user authentication and text mode, and allows you to perform operations on the file system. His main feature is that it allows multiple (in particular, binary) connections. One of the channels is a control channel - through it commands are sent to the server and responses are returned. The rest are used directly for data transfer. At the same time, FTP allows you to reduce traffic costs and time spent on sending large files.

FTP functions

To work with the protocol, standard UNIX commands are used. Their full list can be found by typing “help” or “?” in a special line. The most commonly used commands are:

• open- establishes a connection to an FTP site. Used when accessing different servers during one session. Requires preliminary closing of the previous FTP site with the command close;
• user- is used for re-enter username and password for authentication. The function is necessary in cases where the remote machine allows users with certain parameters;
• bye or quit- used in parallel with close, closes all connections and ends the program;
• remotehelp- opens background information using commands supported by the remote FTP server.

When working with functions, you must adhere to the following rules:

• use the "/" character to separate directories;
• monitor the use of lowercase and capital letters (case is important);
• use prefixes that begin with a period (optional).

Commands and, most often, auxiliary programs for FTP connections allow you to upload files to the server from your computer and vice versa, as well as change access rights to individual objects.

Programs for FTP connection

Specialized software is used for efficient and visual work with FTP servers. Most applications are aimed not only at professionals, but also at beginners who can easily cope with them intuitively. clear interface. Let's consider the most popular programs, performing the functions of FTP clients.

Far Manager

Far Manager - an example of a console file manager, developed for Windows OS Russian programmer Evgeniy Roshal. The program has a recognizable two-window interface and standard blue and white color scheme. Control is carried out through a system of commands entered from the keyboard. When working with FTP, access via Various types proxy servers, searching and replacing characters in multiple files, automatic resuming is triggered. It is freely distributed software.

Total Commander

Total Commander has its own FTP client, which allows you to perform all standard operations with files and folders: copy, cut, create, rename, delete, view, edit. Please note that FTP accesses are saved automatically in the client and are stored unencrypted. Total Commander is free software.

FileZilla

FileZilla is a popular FTP client with open source and multilingual interface. Designed for Windows, Linux and Mac OS. Supports FTP over SSL/TLS (aka FTPS), IPv6, IDN. Works with non-Latin domain zones, is capable of transferring large files (from 4 GB), allows you to configure download and transfer speed limits. Implemented support for Drag-and-drop, remote file editing, working with tabs and the download queue. It is freely distributed software.

WinSCP is a convenient graphical client for working with FTP. Designed for use in a Windows OS environment. It supports copying files in protected mode, automation using scripts, integration with Pageant, and also features a recognizable Norton Commander-style interface. The client provides the ability to save connection settings, synchronize folders using custom algorithms, and has a built-in text editor. It is freely distributed software.

FireFTP is not a standalone application, but an extension for popular browser Mozilla FireFox. Provides access to the FTP server in a separate tab. After installation, the extension can be found in the “Tools” panel. The client works in two-window mode and allows you to perform standard operations: moving, adding, renaming, deleting. Implemented support for multiple accounts, encryption of connections, changing access rights to files and editing them without preload on PC. It is freely distributed software.

A specific client to work with can be selected based on what FTP is needed for and what the tasks of working on the server are.

How to connect to hosting via FTP

Select the appropriate client and install it on your PC. Next, use the following information to log in to your hosting:

• login and password;
• server host or address;
• port for connection (you must specify “21”).

Additionally, you may need to specify the server type and login method. Next, you need to click the button to connect and start working with files and folders. To choose how to open FTP, refer to the previous paragraph.

This article is an attempt to describe the main differences between the well-known FTP and HTTP data exchange protocols.

We have been actively using both protocols in our core product for many years, and during this time we have encountered many misconceptions and misunderstandings about how these two fundamental Internet file sharing protocols work.

If you see any errors or inaccuracies, please write about it.

Disclaimer: V English language There are two terms: “upload” and “download”. Not in Russian good analogues, therefore, for files that we send from the client to the server, we use the word “upload”, and for files that we take to the client from the server, we use the word “download”.

Both protocols are used for downloading and uploading files on the Internet and local networks. For text and binary data. Both protocols run on top of TCP/IP. But there are several major differences between them.

Transmission speed

Probably the most common question is: which is faster for transferring files, FTP or HTTP?

What makes FTP fast?

• there are no meta descriptions in the transmitted stream, only pure binary data. The reference data comes in a separate connection;
• there are no overhead costs for transcoding the transmitted data.

What makes HTTP fast?

• reusing existing persistent connections improves TCP performance without wasting time creating new connections;
• pipeline processing allows you to quickly request multiple files from the same server;
• (automatic) traffic compression reduces the amount of data transferred, this can increase the transfer speed provided that the client and server are fast and the communication channel is slow;
• There are no control commands in the data stream, this saves processing time.

Ultimately the net result depends on the specific details of course, but I would say that for single static files you won't be able to see a noticeable difference.

For a single file of small size and slow connection FTP will perform better. When receiving several files in a row (especially small sizes) HTTP usually shows better results.

Age

Fill

Both protocols can do this. FTP has the “append” command, HTTP follows the approach “here’s the data, and you figure out what to do with it,” that is, there are no commands for managing uploaded files.

It should be said that there is WebDAV protocol, built on top of HTTP, which allows you to work with files in a traditional manner, as if they were on your local device.

ASCII, EBCDIC or binary formats

FTP has an understanding of the file format, so it can transfer data in both ASCII and binary form (raw bytes). HTTP always sends files in binary form. Thus, FTP is able to convert data on the fly if it is transferred between systems with different architectures (Windows/Linux/mainframes).

For example, if the sender uses one scheme to encode the end of a line ("EOL" - End-Of-Line), and the recipient uses another, then FTP will make sure that they understand each other. Unix uses only the NL character (newLine x0A), and MS Windows uses two characters in a row, CR and LF (CarriageReturn and LineFeed - x0D0A). EBCDIC conversions are used on older mainframes.

HTTP, as opposed to FTP, provides metadata for files, "Content-Type". In this way, metadata can be used by clients to interpret the content.

Headings

File transfers over HTTP always include a set of headers that contain metadata. FTP never transfers any headers. In this regard, when transferring large quantity small files, their headers will make up a significant portion of the traffic. IN HTTP headers contains information about the date and time of file modification, character encoding, server name and version, etc.

Pipelines or Conveyors

HTTP supports pipelined data processing. This means that the client can request a new file transfer before the previous one is completed, which makes it possible to eliminate delays when uploading several documents in a row. TCP packets will thus be optimized for maximum speed transfers.

Something similar, although not quite similar, exists in FTP. This is support for multiple requests to fetch files in parallel on a single control connection. Of course, for this you need to use new TCP connections to transfer binary data, one for each file, however, not all FTP servers support such capabilities.

FTP commands/responses

An FTP client can send many commands to the server and receive responses from the server. Even the transfer of one file includes a whole series of such simple commands. This, of course, has a negative impact on speed because each command requires processing on two sides: the client and the server. This causes delays. HTTP data transfer is predominantly only one request and one response (for each file). Receiving a single file via FTP can sometimes take up to a dozen commands and responses between the client and server.

Two connections

One of the most big problems for FTP in real work it is using two connections. The first is for sending control commands, and the second is for transmitting the contents of the file. For this purpose, it opens a separate TCP stream each time. If you transfer 100 files, 100 TCP connections will be opened and closed in turn.

Firewalls and NAT

FTP uses two connections: control and data transfer. The data connection can go in two directions and use dynamic port numbers. This adds headaches to administrators and often requires firewalls to understand the specifics of how FTP works at the network protocol to ensure normal operation.

This also means that if both sides of the connection are behind NAT, you likely won't be able to use FTP.

In addition, NAT kills idle connections through which long time there was no data transfer. Therefore, during long passes over FTP on slow communication channels we find ourselves in a situation where the connection is broken because NAT has decided that it is no longer active.

To prevent this from happening, you have to send dummy empty commands from time to time to keep the connection alive. The result is small but extra traffic.

Active and passive modes

FTP opens a second connection in active or passive mode. If the active mode is running (the connection is initiated by the server), there will be problems with the connection in complex networks, because such a connection is not possible through NAT. Therefore, in most cases, passive mode is used, when the connection occurs only from the client side.

Encrypted control connections

Because firewalls must be able to "pick apart" control FTP connection In order to be able to correctly open a second connection to transfer binary data, there is a huge problem with encrypted connections (FTP-SSL or FTPS). Once the control connection is encrypted, the firewall is no longer able to interpret its commands to understand when and how to allow a second connection between the client and server to transfer binary data.

In addition, the development of the FTPS standard itself took too long, which led to the simultaneous existence of several hybrid versions that are poorly compatible with each other.

Authorization schemes

FTP and HTTP have several documented authentication methods. Both protocols offer basic authentication in plain text (login/password). However, for HTTP there are several commonly used verification methods that do not send the password in plain text, unlike FTP.

Download

Both protocols can do this. Both protocols had problems downloading files larger than 2 gigabytes, but this is a thing of the past. In modern clients and servers, on modern operating systems this problem no longer exists.

Ranges/resuming downloads

FTP supports downloading and uploading, as well as restoring broken connections and continuing transfers in both directions. HTTP can only boast of recovery when downloading, and when uploading files to the server, restoring a broken connection and continuing uploading is often impossible.

Unlike FTP, HTTP supports more advanced download ranges.

FTP also has problems resuming connections when uploading or downloading files starting from a segment larger than 2 GB.

Persistent connections

An HTTP client can maintain one persistent connection to the server for any number of file transfers.

To avoid closing the connection when you are unable to inform the remote party that the file transfer has already been completed, HTTP introduced the so-called encoding of transmitted blocks (chunks) of data.

During transmission, the sending side sends the data stream in blocks (block size + data itself) until they run out, and then transmits a block with zero length to signal the end of the file.

In addition to the fact that the connection does not need to be closed and reopened for new files, another obvious advantage of this scheme is the ability to detect premature emergency shutdowns during the transfer process.

Compression

HTTP gives the server and client the ability to agree and choose one of the compression algorithms. The gzip algorithm is perhaps the most widely used. There is a more modern brotli, but it is not yet fully supported different servers and clients, although it gives better compression(up to +20%), especially on text html, javascript and css files.

FTP provides official built-in RLE compression, however it is generally ineffective for most binary and text data. There are many additional "hack" implementations for compressing FTP traffic, but none of them have become official and widely used.

FXP

FTP supports technology for transferring data from one server to another, as if the transfer was carried out directly by the client. However, on most servers this feature is disabled due to security issues, as the FXP protocol was not well designed.

IPv6

Both HTTP and FTP work fine with IPv6, however, the original FTP protocol specification did not originally have IPv6 support, and because of this, many servers still do not have the necessary commands to turn it on. This also applies firewalls between clients and servers, which must understand FTP.

Name-based shared hosting

Using HTTP 1.1, you can easily host many sites on one server, and they will all be distinguished by their names.

In FTP you cannot use at all virtual hosting based on names until the HOST command is implemented on the server you are connected to. This is a new specification and is not widely used yet.

Browsing Directories

In FTP you can get a list of files from a folder on remote server, without downloading them, while HTTP does not have such an option.

However, due to the fact that the authors of the FTP specification lived in different times, the commands for listing files in a directory (LIST and NLST) do not have a clearly defined output format. Therefore, the authors FTP clients have to do writing parsers text to try to correctly guess what data the server is sending them. More recent specifications (RFC3659) provide new commands such as MLSD, but they are not yet widely used and are poorly supported by different servers and clients.

Lists of files in directories via HTTP are usually transmitted as text in HTML format, or using WebDAV, which runs on top of HTTP.

Proxy support

One of the major advantages of HTTP over FTP is the proxy support built into it from the very beginning. The technology is well established and works very well. Many protocols can be encapsulated inside HTTP, as a kind of “envelope” for passing proxy servers.

FTP has always been used with proxy servers, but it has never been standardized and has always required special approaches on a case-by-case basis.