Since HTTP is a client-server protocol, an HTTP session consists of three phases:

1. The client establishes TCP connections (or another connection if TCP transport is not used).
2. The client sends a request and waits for a response.
3. The server processes the request and sends a response containing the status code and related data.

Starting with HTTP / 1.1, after the third phase, the connection is not closed because the client is allowed to initiate another request. That is, the second and third phases can be repeated.

Establishing a connection

Since HTTP is a client-server protocol, the connection is always established by the client. Opening a connection in HTTP means establishing a connection through the appropriate transport, usually TCP.

In the case of TCP, port 80 is used as the default HTTP server port on the computer, although others are also often used, such as 8000 or 8080. The URL of the loaded page contains the domain name and port, which can be omitted if it matches the default port.

We mean: The client-server model prevents the server from sending data to the client without explicitly requesting that data. To work around this problem, web developers use various techniques: periodically ping the server using the XMLHTTPRequest Javascript object, the HTML WebSockets API, or similar protocols.

Sending a customer request

When the connection is established the user-agent can send a request. (the user-agent is usually a web browser, but it may not be) The client request is text directives separated by CRLF (line break). The request itself includes three blocks:

1. The first lines contain the request method and its parameters:
   • path to document - absolute URL without specifying protocol and domain name
   • HTTP protocol version
2. Each subsequent line is an HTTP header and sends to the server some information about the types of preferred data (for example, what language, what MIME types) or instructions that change the server's behavior (for example, do not send a response if it is already in the cache). These HTTP headers form a block that ends with an empty line.
3. The last block is optional and contains additional data. Mostly used by the POST method.

Examples of requests

We get the main page of the site, and tell the server that the user-agent prefers the page in French, if possible:

GET / HTTP / 1.1 Host: site Accept-Language: fr

Pay attention to the empty line at the end, which separates the data block from the header block. Since the request does not contain the Content-Length: HTTP header, the data block is empty and the server can start processing the request as soon as it receives an empty string indicating the end of the headers.

We send the result of the form submission:

POST /contact_form.php HTTP / 1.1 Host: site Content-Length: 64 Content-Type: application / x-www-form-urlencoded name = Joe% 20User & request = Send% 20me% 20one% 20of% 20your% 20catalogue

Request Methods

HTTP defines a set of request methods indicating the desired action on the resource. Although they can also be nouns, these request methods are sometimes referred to as HTTP commands. The most common GET and POST requests are:

• GET is used to request the content of the specified resource. A request using GET should only receive data.
• The POST method sends data to the server so that it can change its state. This method is often used for HTML forms.

Server response structure

After the attached agent has sent its request, the web server processes it and sends a response. By analogy with a client request, the server response is text directives separated by CRLF, grouped into three different blocks:

1. The first line - the status line, consists of a confirmation of the used HTTP version and the status of the request (and its value in a human-readable form).
2. Subsequent lines are HTTP headers that give the client some information about the data being sent (eg type, size, compression algorithm, caching hints). As with the client request, these HTTP headers form a block that ends with an empty line.
3. The last block contains data (if any).

Sample responses

Successful web page retrieval:

HTTP / 1.1 200 OK Date: Sat, 09 Oct 2010 14:28:02 GMT Server: Apache Last-Modified: Tue, 01 Dec 2009 20:18:22 GMT ETag: "51142bc1-7449-479b075b2891b" Accept-Ranges: bytes Content-Length: 29769 Content-Type: text / html(here goes 29769 bytes of the requested webpage)

The message that the requested resource has been moved:

HTTP / 1.1 301 Moved Permanently Server: Apache / 2.2.3 (Red Hat) Content-Type: text / html; charset = iso-8859-1 Date: Sat, 09 Oct 2010 14:30:24 GMT Location: (this is the new address of the requested resource, the client is expected to request it) Keep-Alive: timeout = 15, max = 98 Accept-Ranges: bytes Via: Moz-Cache-zlb05 Connection: Keep-Alive X-Cache-Info: caching X-Cache-Info: caching Content-Length: 325 (The content contains a standard page that will be shown if the client is unable to follow the link)

Moved Permanently

The document has moved here.

---

Apache / 2.2.3 (Red Hat) Server at Port 80 site

The message that the requested resource does not exist:

Sessions in PHP are a mechanism for storing information about the client's computer on the server side. In fact, sessions in PHP are not such a complex topic, but to understand it, you need to know how cookies work in PHP. So, if you do not know how cookies work in PHP, then first read the corresponding article, and then come back here.

The word session is translated from English as a session, so the very meaning of sessions in PHP becomes clearer, but the term "sessions" has stuck among programmers, and we will use it in this article.

Sessions in PHP are very similar to the cookie mechanism, the same key => value pairs, only they are stored on the server side.

Session_start () function

We need to start the session, for this there is the session_start () function. This function starts a session, or session, whatever you call it.

It is desirable to call the session_start () function at the very beginning of the page, but in my examples I do not.

$ _SESSION array

Sessions are groups of variables that are stored on the server but refer to one unique visitor. Again, this is the key point: sessions are stored on the server.

In order to ensure the interaction of each visitor with his data from his session, a cookie is used, the command to create which PHP gives itself, you do not need to worry about it. This cookie is only meaningful to the server and cannot be used to retrieve user data.

On the server, session data is stored in a text file and is available in the PHP program in the $ _SESSION array. To save a variable in a session, you need to assign a value to it in this array.

Let's finally start using examples. Everything is very simple.

value. ";?>

Now let's try to get the value from the $ _SESSION array in another example.

Please note that if in the second example we remove the session_start () function, then we will not have access to the data of the $ _SESSION array.

Session_id () function

After the session is created, you automatically access the unique session identifier using the session_id () function. This function allows you to both set and get the value of the session identifier.

You can look in the toolbar for developers of your browser (in Chrome for this, press Ctrl + Shift + I, then Resources, and there you will find a cookie), this domain put a cookie for your browser with the name PHPSESSID and something like this: "7g5df9rkd1hhvr33lq1k6c72p7".

It is by the value of PHPSESSID that the server will determine your browser and work with the corresponding set of variables that will be available to the script through the $ _SESSION array, as mentioned earlier.

Session_name () function

If the session_id () function allows you to get the value of the session identifier, the session_name () function allows you to get the name of the session.

Once again about the session_start () function

Now we know more about the mix-up of sessions in PHP and we need to return to the session_start () function again. This function initializes the session mechanism for the current user. How exactly does this happen:

• If the user has launched the site for the first time, then session_start () sets a cookie on the client and creates a temporary storage on the server associated with the user ID.
• Defines the store associated with the passed current identifier.
• If there is data in storage on the server, it is placed in the $ _SESSION array.
• If register_globals from the php.ini file is On, then all elements of the $ _SESSION array become global variables.

Session usage example

Now we will look at an example that will allow you to do a little experimenting with sessions.

Counter

In the current session, you have opened the pageonce.

Open the example in "> this tab.

All work of sessions is based on the $ _SESSION array, this is clearly seen in this example.

If you close the browser window, the session will end, our counter will be reset to zero. This behavior of sessions in PHP can be changed, we will return to this issue a little further in the article.

End of session

In order to end the session, we need:

1. Clear the $ _SESSION array.
2. Delete temporary storage on the server.
3. Delete session cookie.

You can clear the $ _SESSION array using the session_unset () function.

The session_destroy () function removes temporary storage on the server. By the way, she doesn't do anything else.

You need to remove the session cookie using the setcookie () function, which we learned in the lesson working with cookies in PHP.

Session termination example:

The session has ended.

Now you can experiment: run the example with the counter in one window, wind up the counter, and then run the example with deleting the session and refresh the page with the counter again.

Deleting a cookie can be done like this:

setcookie (session_name (), "", time () - 60 * 60 * 24 * 32, "/")

Once again about the session_name () and session_id () functions

The session_name () and session_id () functions are rarely used in practice, but I am writing about them, since the article needs to reveal the very mechanism of the sessions in PHP.

You can use these functions to define your own names and session IDs, but this is not recommended. If you want to set them, then write these functions with arguments before the session_start () function, as in the example below:

Using this example, all users will be assigned the same session ID.

Let's stop here in more detail, if you run the example from the section about the session_name () function (here is the link) in different browsers (for example, in Chrome and Internet Explorer), then each browser will have its own unique session identifier. Browsers store cookies each in their own folder, so the session_start () function will give each browser its own unique identifier and, accordingly, a unique storage will be created for each browser on the server. Therefore, the counter example (this one) will work independently of each other in each browser.

If you set the same session identifier for all users, then they will work with the same repository on the server. Here's an example of a counter that will count visits from different browsers:

100) (session_unset (); session_destroy ();)?>

Counter number 2

Opened the page in different browsersonce.

Open the example in "> this tab.

If you run this example, it is not a fact that you will see a unit there. Other visitors may have already changed the values ​​in the session store on the server. I don't know when the server deletes the storage in this case, so if the counter exceeds 100, I will end the session.

Setting the waiting time

By default, the session "lives" until the visitor closes the browser window. This is due to the fact that the session_start () function sets such a cookie to the client.

The session lifetime can be changed using the session_set_cookie_params () function, here is its syntax.

session_set_cookie_params (int lifetime [, string path [, string domain [, bool secure]]])

In practice, it is enough to use only the first parameter (lifetime), here you write down the time in seconds, which determines how much the server should remember the session state after closing the browser.

The session_set_cookie_params () function applies only to the duration of the script.

Here's an example using this function:

Counter No. 3

Counter value:.

Open counter in "> this tab.

Wind up the counter and close the browser, after 30 seconds open this example again. Your session will be saved.

What is a session?

In computer technology, in particular when organizing networks, a session is called an almost invariable interactive exchange of information, also known as a connection or a dialogue between two interacting devices or between a user and a computer (see the topic Identification procedure). The session is established at a certain time and is interrupted after a certain period. During an established session, more than one message is transmitted in each direction. Typically, a session is stable, that is, at least one of the interacting parties must store information about the session history in order to maintain the ability to exchange information, as opposed to stateless exchange, the essence of which is the exchange of independent requests and responses.

Connection sessions can be part of the protocols or services at the application level, session or transport layers of the OSI model.

The router uses a table of sessions to store information about them. The table takes up some of the memory and CPU resources for functions such as counting sessions. The session size in the table is fixed; if it overflows, the router is unable to transmit information even if there is an outgoing data stream.

Let's try to explain the purpose of the session with the following examples.

1. When you open a website like www .. Everything happens in just a minute, so you don't need to worry about the speed of your Internet connection. But why, then, are so many sessions needed? The site contains various information - many pictures, videos. In order to open a page in a browser, you need to download them to a temporary folder on your computer.

2. When we download via BT, it requires a lot of sessions. During initialization, approximately 2000 sessions are required, but their number will decrease with a stable load. The list of sessions below shows the number of current sessions at the corresponding speed of incoming and outgoing downloads via BT.

It also happens when using other P2P software as they work in a similar way.

Please note that there is no clear relationship between speed and number of sessions. If there are a large number of sessions, the speed will not always be high, just as the presence of a high speed does not mean the presence of a large number of sessions. But, in general, when there are many sessions, the speed is higher.

Why set a session limit?

1) This avoids network slowdowns as P2P software is limited in the number of sessions.

2) This avoids the consumption of network resources by any virus or other type of network attacks that require a large number of sessions.

How to set up session restriction on the routerTP- LINK ?

Step 1

Open a browser and enter the network IP address of the router into the address bar; the default is 192.168.1.1, then press Enter.

Step 2

Enter the username and password to enter the web interface; by default, both login and password are admin.

Step 3

Click Session Limit -> Session Limit on the left side of the page, activate the Session Limit function, then click the Save button to save the settings.

Step 4

Click Add New to configure the session limitation rule, enter the network IP address of the computer you want to limit and set the maximum number of sessions (Max Session).

Note

Max Session is an individual limit for a specific computer, even if you entered an array of network addresses.

Text / html 10/19/2017 7:51:00 AM Vector BCO 0

There are 13-15 clients sitting on the WS2012 terminal server. The terminal on the virtual machine is spinning. On a separate virtual machine DNS, AD and DHCP.

Question # 1: how to set the disconnect time limit when the session is inactive?

In gpedit.msc Computer Configuration -> Windows Components -> Remote Desktop Services -> Remote Desktop Session Host -> Limit Sessions by Time. All parameters are there - not specified. And while idle in the region of 20-30 minutes. throws out everyone.

I rummaged through a lot of information in Runet, I didn't find it for WS2012, there is only for WS2003

Question number 2: how to make sure that after disconnecting the session, all software open for the user is not closed?

Those. the user, for example, should be thrown out after 20 minutes, while his entire session is killed and when he re-enters all his open programs and docks, they are closed. In fact, when there is an answer to question number 1, I will set the time, but still I would like the user not to reopen everything, after each miscarriage ... I understand that this is related to the life of the session, but still, is there a mode with which session dies, but its state persists? And if so, how do you set it up?

Question # 3: Is it possible to restrict the rights to shutdown the server in WS2012?

And then when users press the start, they have a tiled panel and there is a "power" button, that is. any user can mistakenly extinguish the terminal server and all the work gets up.

Moderator

Text / html 10/19/2017 11:30:36 AM Avksentyev Sergey 1

1 So in the properties of the collection there is a tab "Session" There and see what you need to configure .. Or I did not understand?

2 It depends on how the user closes the session .. If you disable and configure not to close the disabled senas, then I will remain open programs .. BUT something seems to me this is generally not a very good idea ... this remaining open bullshit was closing.

3 If your users are not admins, then .. in this button, by default, just disable and exit ..

• Text / html 10/23/2017 10:51:31 AM Ivan end KO 0

  >> How did you set up the terminal server? If you have the RDS role configured, and until the session is completely closed (with all user programs in this session).

  >> If you have an RDS role configured

  Don't know where to look?

  >> in the configuration of the collection there is a session lifetime until the moment of disconnection

  Don't know where to look?

  >> Do you have users on the server that are administrators?

  Yes, admins.

  >> By default, regular users cannot shutdown the server. But you can hide this button in politics altogether.

• Text / html 10/23/2017 11:00:12 AM Ivan end KO 0

  >> So in the properties of the collection there is a tab "Session" There and see what you need to configure .. Or I didn't understand?

  Perhaps you understood correctly, but I don't know how to do it, that's why I'm writing here ... for some reason I can't really find instructions on how to set up a terminal server, by roles and sessions in runet.

  You wrote in the properties of the collection - where is this?

  >> It depends on how the user closes the session .. If you disable and configure not to close the disconnected session, then the programs will remain open .. BUT something seems to me this is generally not a very good idea ... all this leftover open-ended bullshit was shutting down.

  I would just increase the lifetime of the session, to begin with ... I perfectly understand what you are talking about, hanging sessions are not the case. I just want to know where exactly all this stuff is set up ...?

  I have no experience in setting up a terminal server (previously I worked in it only as a client), although I have been in the IT structure for a long time, but I have never done this very task. And I would not write a question here if I could find detailed instructions for execution on the internet ...

• Text / html 10/23/2017 11:13:30 AM Vector BCO 0

  >> How did you set up the terminal server? If you have configured the RDS role in the collection configuration, there is a session lifetime until the moment of disconnection, and until the moment when the session is completely closed (with all user programs in this session).

  Favorite but very strange, for me, question - how did you set up? As I think from the questions it should be clear that it was not me who set up. Otherwise, it is very difficult to explain what I set up, and now I don't know how to change ... amnesia, etc.

  Once again, it was not me who set up. And since it was not me who did it, then the skills in these settings are clearly not enough. So I ask a question to professionals: how to do it, please tell me?

  >> If you have an RDS role configured

  Don't know where to look?

  >> in the configuration of the collection there is a session lifetime until the moment of disconnection

  Don't know where to look?

  >> Do you have users on the server that are administrators?

  Yes, admins.

  >> By default, regular users cannot shutdown the server. But you can hide this button in politics altogether.

  How to remove admin rights from users? Is it configurable by AD or elsewhere on the terminal server? How do I make the policy hide the power button?

  Thank you in advance for your understanding and waiting for your answers ...

  You have a mega progressive tool on your server called " Server Manager"roles / features are added / removed in it, and they are configured there. Check out the functionality of this tool. On the left there are settings for some roles (installed). If there is an RDS item, go to it, and then to the collection settings. Google how the terminal server is configured on WS 2012 r2. You can search like this Google -> "Terminal server 2012 r2 step by step guide".

  On the server (and not only on the server) there is also a mega tool called Computer Management(not to be confused with Server Manager) you can find it by clicking the right mouse button on the start.

  In Computer Management, go to Local users and groups, then to groups, then to administrators, and see who is sitting there and why. Throw out all who do not need these rights. and reboot the server (make sure that you have not taken away your rights, there will be a quest to get them back later).

  How to hide Google button -> "Hide shut down button GPO"

  The opinion expressed by me is not an official position of Microsoft

  Moderator

  Text / html 10/25/2017 7:51:20 AM Ivan end KO 0

  >> It was difficult to guess that you do not know how to manage the server, since as a rule, those who come here at least google their question first.

  The question was googled and not once, I wrote above. Only I googled on Russian-language resources ... There are practically no sensible articles there. I myself saw that there are English sources, but the skills of technical English are not good enough to 100% correctly understand large articles about setting up the system from scratch, which I have never done before.

  >>You can search Google -> "Terminal server 2012 r2 step by step guide. Google -> "Hide shut down button GPO

  I know how to use Google, but I don't need to learn how to use a search engine. Why didn't I look in English-language sources - I wrote above ... If you are told that they do not know how to set up a terminal server, this does not mean that a person cannot google. But you did not miss the opportunity, as 99% of IT pros, to start with moralizing and teaching a person to google. As for me, this has always been and is a problem in the understanding of people with it infrastructure. A good show-off is more expensive than money. And more than one IT specialist does not miss this, as practice shows, even when communicating with colleagues, so to speak.

  The question was asked - how to set up a terminal server? And it is explained in detail what and where to configure ... and you write to me about Google requests. I asked a man about mathematics, and he started about the weather ... so it turns out. Instead of everything that you wrote above, you could give a short answer in Russian, period. Yes, you can tell me that googling the issue that needs to be resolved is more related subjects. Yes, and this is true, but if you read carefully the first message, then your this term would not be needed.

  >> You have a mega progressive tool on your server called "Server Manager".

  Here you can read a moralizing tone, more willing to measure themselves in a famous place, in front of a person. It's like prof. a boxer will show a beginner how to do a knockout, on his face and without preparation ... a very strange method, help a person and answer questions.

  Your form here is in Russian, the question was in Russian, and I would like to receive the answer in Russian.

  Without preachings - why didn't you google? And there is such a trump button Google, etc.

  It is much more productive to work in style: question - answer.

  Question: How to set up one? Answer: go there and do this.

• Text / html 10/25/2017 8:25:04 AM Vector BCO 0

  On " question - how to set up a terminal server"you can reply with articles of 10-15 pages - this is not a forum format. I gave you specific queries in a search engine that will lead you to a guaranteed result. There is also a lot of information on Russian-language resources, for example, on habr and similar sites, if you do not find it, then look at you still turn out badly.

  In order to give a clear answer, you need to get a clear question. I asked you not preachy the question in the first message was answered in the style of " What are you asking me nonsense, it is still clearly written that I xs what is going on".

  The opinion expressed by me is not an official position of Microsoft

Session (from Latin - sessio - meeting, English - session) is a period of time that covers the user's work on the Internet from the moment of opening the first to the last links. It is calculated as the difference in time between the initial and final requests. However, the last page can be viewed by the user for different times, from which, therefore, measuring the time between two requests becomes more difficult.

How session is related to HTTP and COOKIES

What a session is can be explained in terms of the HTTP protocol. By itself, this protocol does not provide a way to maintain state between two operations. That is, in other words, by opening one page and then going from it to another, HTTP will not be able to establish that both requests belong to the same user. And this is where a special tracking method comes to the rescue - session management (our sessions).
Hence, answering the question of what a session is, we can say that it is an auxiliary logical object that facilitates the transfer of data between successive HTTP requests from one user.
Cookies, like the session, store information about the user as he navigates through different pages and improve the operation of the protocol. But unlike the second, where data is stored in temporary files on the server, they save them on the user's computer in the form of small fragments.

What are sessions for?

The use of sessions becomes indispensable when working with sites such as forums, message boards and online stores, because in this case it is necessary to save user data over several pages.

Session stages

The entire session can be divided into three stages:

• opening a session (when a user starts working with a specific site),
• accounting for session variables (when going to different pages),
• end of the session.

Due to the fact that session data is stored on a third-party server, it is best not to store large amounts of information in them, but to use cookies.