msgid "" msgstr "" "Project-Id-Version: English (cnp3-ebook)\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-04-18 16:42+0200\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: English \n" "Language: en\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=2; plural=n != 1;\n" "X-Generator: Weblate 5.14.3\n" #: ../../protocols/http.rst:7 #, read-only msgid "The HyperText Transfer Protocol" msgstr "The HyperText Transfer Protocol" #: ../../protocols/http.rst:9 #, read-only msgid "" "In the early days, the Internet was mainly used for remote terminal access " "with telnet_, email and file transfer. The default file transfer protocol, " "`FTP`, defined in :rfc:`959` was widely used. `FTP` clients and servers are " "still included in some operating systems." msgstr "" "In the early days, the Internet was mainly used for remote terminal access " "with telnet_, email and file transfer. The default file transfer protocol, " "`FTP`, defined in :rfc:`959` was widely used. `FTP` clients and servers are " "still included in some operating systems." #: ../../protocols/http.rst:11 #, read-only msgid "" "Many `FTP` clients offered a user interface similar to a Unix shell and " "allowed clients to browse the file system on the server and to send and " "retrieve files. `FTP` servers can be configured in two modes :" msgstr "" "Many `FTP` clients offered a user interface similar to a Unix shell and " "allowed clients to browse the file system on the server and to send and " "retrieve files. `FTP` servers can be configured in two modes :" #: ../../protocols/http.rst:13 #, read-only msgid "" "`authenticated` : in this mode, the ftp server only accepts users with a " "valid user name and password. Once authenticated, they can access the files " "and directories according to their permissions" msgstr "" "`authenticated` : in this mode, the ftp server only accepts users with a " "valid user name and password. Once authenticated, they can access the files " "and directories according to their permissions" #: ../../protocols/http.rst:14 #, read-only msgid "" "`anonymous` : in this mode, clients supply the `anonymous` user identifier " "and their email address as password. These clients are granted access to a " "special zone of the file system that only contains public files." msgstr "" "`anonymous` : in this mode, clients supply the `anonymous` user identifier " "and their email address as password. These clients are granted access to a " "special zone of the file system that only contains public files." #: ../../protocols/http.rst:16 #, read-only msgid "" "`FTP` was very popular in the 1990s and early 2000s, but today it has mostly " "been superseded by more recent protocols. Authenticated access to files is " "mainly done by using the Secure Shell (ssh_) protocol defined in :rfc:`4251` " "and supported by clients such as scp_ or sftp_. Nowadays, anonymous access " "is mainly provided by web protocols." msgstr "" "`FTP` was very popular in the 1990s and early 2000s, but today it has mostly " "been superseded by more recent protocols. Authenticated access to files is " "mainly done by using the Secure Shell (ssh_) protocol defined in :rfc:`4251` " "and supported by clients such as scp_ or sftp_. Nowadays, anonymous access " "is mainly provided by web protocols." #: ../../protocols/http.rst:18 #, read-only msgid "" "In the late 1980s, high energy physicists working at CERN_ had to " "efficiently exchange documents about their ongoing and planned experiments. `" "Tim Berners-Lee`_ evaluated several of the documents sharing techniques that " "were available at that time [B1989]_. As none of the existing solutions met " "CERN's requirements, they chose to develop a completely new document sharing " "system. This system was initially called the `mesh`. It was quickly renamed " "the `world wide web`. The starting point for the `world wide web` are " "hypertext documents. An hypertext document is a document that contains " "references (hyperlinks) to other documents that the reader can immediately " "access. Hypertext was not invented for the world wide web. The idea of " "hypertext documents was proposed in 1945 [Bush1945]_ and the first " "experiments were done during the 1960s [Nelson1965]_ [Myers1998]_ . Compared " "to the hypertext documents that were used in the late 1980s, the main " "innovation introduced by the `world wide web` was to allow hyperlinks to " "reference documents stored on different remote machines." msgstr "" "In the late 1980s, high energy physicists working at CERN_ had to " "efficiently exchange documents about their ongoing and planned experiments. `" "Tim Berners-Lee`_ evaluated several of the documents sharing techniques that " "were available at that time [B1989]_. As none of the existing solutions met " "CERN's requirements, they chose to develop a completely new document sharing " "system. This system was initially called the `mesh`. It was quickly renamed " "the `world wide web`. The starting point for the `world wide web` are " "hypertext documents. An hypertext document is a document that contains " "references (hyperlinks) to other documents that the reader can immediately " "access. Hypertext was not invented for the world wide web. The idea of " "hypertext documents was proposed in 1945 [Bush1945]_ and the first " "experiments were done during the 1960s [Nelson1965]_ [Myers1998]_ . Compared " "to the hypertext documents that were used in the late 1980s, the main " "innovation introduced by the `world wide web` was to allow hyperlinks to " "reference documents stored on different remote machines." #: ../../protocols/http.rst:46 #, read-only msgid "" "A document sharing system such as the `world wide web` is composed of three " "important parts." msgstr "" "A document sharing system such as the `world wide web` is composed of three " "important parts." #: ../../protocols/http.rst:48 #, read-only msgid "" "A standardized addressing scheme that unambiguously identifies documents" msgstr "" "A standardized addressing scheme that unambiguously identifies documents" #: ../../protocols/http.rst:49 #, read-only msgid "" "A standard document format : the `HyperText Markup Language `_" msgstr "" "A standard document format : the `HyperText Markup Language `_" #: ../../protocols/http.rst:50 #, read-only msgid "" "A standardized protocol to efficiently retrieve the documents stored on a " "server" msgstr "" "A standardized protocol to efficiently retrieve the documents stored on a " "server" #: ../../protocols/http.rst:53 #, read-only msgid "Open standards and open implementations" msgstr "Open standards and open implementations" #: ../../protocols/http.rst:55 #, read-only msgid "" "Open standards play a key role in the success of the `world wide web` as we " "know it today. Without open standards, the world wide web would have never " "reached its current size. In addition to open standards, another important " "factor for the success of the web was the availability of open and efficient " "implementations of these standards. When CERN started to work on the `web`, " "their objective was to build a running system that could be used by " "physicists. They developed open-source implementations of the `first web " "servers `_ and `web clients `_. These open-source implementations were powerful " "and could be used as is, by institutions willing to share information. They " "were also extended by other developers who contributed to new features. For " "example, the NCSA_ added support for images in their `Mosaic browser `_ that was eventually used to " "create `Netscape Communications `_ " "and the first commercial browsers and servers." msgstr "" "Open standards play a key role in the success of the `world wide web` as we " "know it today. Without open standards, the world wide web would have never " "reached its current size. In addition to open standards, another important " "factor for the success of the web was the availability of open and efficient " "implementations of these standards. When CERN started to work on the `web`, " "their objective was to build a running system that could be used by " "physicists. They developed open-source implementations of the `first web " "servers `_ and `web clients `_. These open-source implementations were powerful " "and could be used as is, by institutions willing to share information. They " "were also extended by other developers who contributed to new features. For " "example, the NCSA_ added support for images in their `Mosaic browser `_ that was eventually used to " "create `Netscape Communications `_ " "and the first commercial browsers and servers." #: ../../protocols/http.rst:58 #, read-only msgid "" "The first components of the `world wide web` are the Uniform Resource " "Identifiers (URI), defined in :rfc:`3986`. A URI is a character string that " "unambiguously identifies a resource on the world wide web. Here is a subset " "of the BNF for URIs ::" msgstr "" "The first components of the `world wide web` are the Uniform Resource " "Identifiers (URI), defined in :rfc:`3986`. A URI is a character string that " "unambiguously identifies a resource on the world wide web. Here is a subset " "of the BNF for URIs ::" #: ../../protocols/http.rst:75 #, read-only msgid "" "The first component of a URI is its `scheme`. A `scheme` can be seen as a " "selector, indicating the meaning of the fields after it. In practice, the " "scheme often identifies the application-layer protocol that must be used by " "the client to retrieve the document, but it is not always the case. Some " "schemes do not imply a protocol at all and some do not indicate a " "retrievable document [#furiretrieve]_. The most frequent schemes are `http` " "and `https`. We focus on `http` in this section. A URI scheme can be defined " "for almost any application layer protocol [#furilist]_. The characters `:` " "and `//` follow the `scheme` of any URI." msgstr "" "The first component of a URI is its `scheme`. A `scheme` can be seen as a " "selector, indicating the meaning of the fields after it. In practice, the " "scheme often identifies the application-layer protocol that must be used by " "the client to retrieve the document, but it is not always the case. Some " "schemes do not imply a protocol at all and some do not indicate a " "retrievable document [#furiretrieve]_. The most frequent schemes are `http` " "and `https`. We focus on `http` in this section. A URI scheme can be defined " "for almost any application layer protocol [#furilist]_. The characters `:` " "and `//` follow the `scheme` of any URI." #: ../../protocols/http.rst:77 #, read-only msgid "" "The second part of the URI is the `authority`. With retrievable URIs, this " "includes the DNS name or the IP address of the server where the document can " "be retrieved using the protocol specified via the `scheme`. This name can be " "preceded by some information about the user (e.g. a user name) who is " "requesting the information. Earlier definitions of the URI allowed the " "specification of a user name and a password before the `@` character " "(:rfc:`1738`), but this is now deprecated as placing a password inside a URI " "is insecure. The host name can be followed by the semicolon character and a " "port number. A default port number is defined for some protocols and the " "port number should only be included in the URI if a non-default port number " "is used (for other protocols, techniques like service DNS records can used)." msgstr "" "The second part of the URI is the `authority`. With retrievable URIs, this " "includes the DNS name or the IP address of the server where the document can " "be retrieved using the protocol specified via the `scheme`. This name can be " "preceded by some information about the user (e.g. a user name) who is " "requesting the information. Earlier definitions of the URI allowed the " "specification of a user name and a password before the `@` character " "(:rfc:`1738`), but this is now deprecated as placing a password inside a URI " "is insecure. The host name can be followed by the semicolon character and a " "port number. A default port number is defined for some protocols and the " "port number should only be included in the URI if a non-default port number " "is used (for other protocols, techniques like service DNS records can used)." #: ../../protocols/http.rst:80 #, read-only msgid "" "The third part of the URI is the path to the document. This path is " "structured as filenames on a Unix host (but it does not imply that the files " "are indeed stored this way on the server). If the path is not specified, the " "server will return a default document. The last two optional parts of the " "URI are used to provide a query parameter and indicate a specific part " "(e.g. a section in an article) of the requested document. Sample URIs are " "shown below." msgstr "" "The third part of the URI is the path to the document. This path is " "structured as filenames on a Unix host (but it does not imply that the files " "are indeed stored this way on the server). If the path is not specified, the " "server will return a default document. The last two optional parts of the " "URI are used to provide a query parameter and indicate a specific part " "(e.g. a section in an article) of the requested document. Sample URIs are " "shown below." #: ../../protocols/http.rst:91 #, read-only msgid "" "The first URI corresponds to a document named `rfc3986.html` that is stored " "on the server named `tools.ietf.org` and can be accessed by using the `http` " "protocol on its default port. The second URI corresponds to an email " "message, with subject `current-issue`, that will be sent to user `infobot` " "in domain `example.com`. The `mailto:` URI scheme is defined in :rfc:`2368`. " "The third URI references the portion `BaseHTTPServer.BaseHTTPRequestHandler` " "of the document `basehttpserver.html` that is stored in the `library` " "directory on the `docs.python.org` server. This document can be retrieved by " "using the `http` protocol. The query parameter `highlight=http` is " "associated to this URI. The fourth example is a server that operates the " "telnet_ protocol, uses IPv6 address `2001:db8:3080:3::2` and is reachable on " "port 2323. The last URI is somewhat special. Most users will assume that it " "corresponds to a document stored on the `cnn.example.com` server. However, " "to parse this URI, it is important to remember that the `@` character is " "used to separate the user name from the host name in the authorization part " "of a URI. This implies that the URI points to a document named " "`top_story.htm` on the host having IPv4 address `10.0.0.1`. The document " "will be retrieved by using the `ftp` protocol with the user name set to " "`cnn.example.com&story=breaking_news`." msgstr "" "The first URI corresponds to a document named `rfc3986.html` that is stored " "on the server named `tools.ietf.org` and can be accessed by using the `http` " "protocol on its default port. The second URI corresponds to an email " "message, with subject `current-issue`, that will be sent to user `infobot` " "in domain `example.com`. The `mailto:` URI scheme is defined in :rfc:`2368`. " "The third URI references the portion `BaseHTTPServer.BaseHTTPRequestHandler` " "of the document `basehttpserver.html` that is stored in the `library` " "directory on the `docs.python.org` server. This document can be retrieved by " "using the `http` protocol. The query parameter `highlight=http` is " "associated to this URI. The fourth example is a server that operates the " "telnet_ protocol, uses IPv6 address `2001:db8:3080:3::2` and is reachable on " "port 2323. The last URI is somewhat special. Most users will assume that it " "corresponds to a document stored on the `cnn.example.com` server. However, " "to parse this URI, it is important to remember that the `@` character is " "used to separate the user name from the host name in the authorization part " "of a URI. This implies that the URI points to a document named " "`top_story.htm` on the host having IPv4 address `10.0.0.1`. The document " "will be retrieved by using the `ftp` protocol with the user name set to " "`cnn.example.com&story=breaking_news`." #: ../../protocols/http.rst:94 #, read-only msgid "" "The second component of the `word wide web` is the HyperText Markup Language " "(HTML). HTML defines the format of the documents that are exchanged on the " "`web`. The `first version of HTML `_ was derived from the " "Standard Generalized Markup Language (SGML) that was standardized in 1986 by " ":term:`ISO`. SGML_ was designed to support large documents maintained by " "government, law firms or aerospace companies that must be shared efficiently " "in a machine-readable manner. These industries require documents to remain " "readable and editable for tens of years and insisted on a standardized " "format supported by multiple vendors. Today, SGML_ is no longer widely used " "beyond specific applications, but its descendants including :term:`HTML` and " ":term:`XML` are now widespread." msgstr "" "The second component of the `word wide web` is the HyperText Markup Language " "(HTML). HTML defines the format of the documents that are exchanged on the " "`web`. The `first version of HTML `_ was derived from the " "Standard Generalized Markup Language (SGML) that was standardized in 1986 by " ":term:`ISO`. SGML_ was designed to support large documents maintained by " "government, law firms or aerospace companies that must be shared efficiently " "in a machine-readable manner. These industries require documents to remain " "readable and editable for tens of years and insisted on a standardized " "format supported by multiple vendors. Today, SGML_ is no longer widely used " "beyond specific applications, but its descendants including :term:`HTML` and " ":term:`XML` are now widespread." #: ../../protocols/http.rst:96 #, read-only msgid "" "A markup language is a structured way of adding annotations about the " "formatting of the document within the document itself. Example markup " "languages include troff_, which is used to write the Unix man pages or " "Latex_. HTML uses markers to annotate text and a document is composed of `" "HTML elements`. Each element is usually composed of three parts: a start tag " "that potentially includes some specific attributes, some text " "(often including other elements), and an end tag. A HTML tag is a keyword " "enclosed in angle brackets. The generic form of an HTML element is ::" msgstr "" "A markup language is a structured way of adding annotations about the " "formatting of the document within the document itself. Example markup " "languages include troff_, which is used to write the Unix man pages or " "Latex_. HTML uses markers to annotate text and a document is composed of `" "HTML elements`. Each element is usually composed of three parts: a start tag " "that potentially includes some specific attributes, some text " "(often including other elements), and an end tag. A HTML tag is a keyword " "enclosed in angle brackets. The generic form of an HTML element is ::" #: ../../protocols/http.rst:100 #, read-only msgid "" "More complex HTML elements can also include optional attributes in the start " "tag ::" msgstr "" "More complex HTML elements can also include optional attributes in the start " "tag ::" #: ../../protocols/http.rst:104 #, read-only msgid "" "The HTML document shown below is composed of two parts: a header, delineated " "by the `` and `` markers, and a body " "(between the `` and `` markers). In the example below, the " "header only contains a title, but other types of information can be included " "in the header. The body contains an image, some text and a list with three " "hyperlinks. The image is included in the web page by indicating its URI " "between brackets inside the `` marker. It is important to " "note that the image can reside on any server. The client will automatically " "download it when rendering the web page. The `

...

` marker is used " "to specify the first level of headings. The `
    ` marker indicates an " "unnumbered list while the `
  • ` marker indicates a list item. The `text` indicates a hyperlink. The `text` will be underlined in " "the rendered web page and the client will fetch the specified URI when the " "user clicks on the link." msgstr "" "The HTML document shown below is composed of two parts: a header, delineated " "by the `` and `` markers, and a body " "(between the `` and `` markers). In the example below, the " "header only contains a title, but other types of information can be included " "in the header. The body contains an image, some text and a list with three " "hyperlinks. The image is included in the web page by indicating its URI " "between brackets inside the `` marker. It is important to " "note that the image can reside on any server. The client will automatically " "download it when rendering the web page. The `

    ...

    ` marker is used " "to specify the first level of headings. The `
      ` marker indicates an " "unnumbered list while the `
    • ` marker indicates a list item. The `text` indicates a hyperlink. The `text` will be underlined in " "the rendered web page and the client will fetch the specified URI when the " "user clicks on the link." #: ../../protocols/http.rst:110 #, read-only msgid "A simple HTML page" msgstr "A simple HTML page" #: ../../protocols/http.rst:112 #, read-only msgid "" "Over the years, various extensions to HTML have been proposed and " "implemented. These include the specification of style sheets that adjust the " "layout of the document and the possibility of adding or referencing " "javascript code. Additional details about the various extensions to HTML may " "be found in the `official specifications `_ " "maintained by W3C_." msgstr "" "Over the years, various extensions to HTML have been proposed and " "implemented. These include the specification of style sheets that adjust the " "layout of the document and the possibility of adding or referencing " "javascript code. Additional details about the various extensions to HTML may " "be found in the `official specifications `_ " "maintained by W3C_." #: ../../protocols/http.rst:114 #, read-only msgid "" "The third component of the `world wide web` is the HyperText Transfer " "Protocol (HTTP). HTTP is a text-based protocol like SMTP. The client sends a " "request and the server returns a response. HTTP runs above the bytestream " "service and HTTP servers listen by default on port `80`. The design of HTTP " "has largely been inspired by the Internet email protocols. Each HTTP request " "contains three parts :" msgstr "" "The third component of the `world wide web` is the HyperText Transfer " "Protocol (HTTP). HTTP is a text-based protocol like SMTP. The client sends a " "request and the server returns a response. HTTP runs above the bytestream " "service and HTTP servers listen by default on port `80`. The design of HTTP " "has largely been inspired by the Internet email protocols. Each HTTP request " "contains three parts :" #: ../../protocols/http.rst:116 #, read-only msgid "" "a `method`, that indicates the type of request, a URI, and the version of " "the HTTP protocol used by the client" msgstr "" "a `method`, that indicates the type of request, a URI, and the version of " "the HTTP protocol used by the client" #: ../../protocols/http.rst:117 #, read-only msgid "" "a `header`, that is used by the client to specify optional parameters for " "the request. An empty line is used to mark the end of the header" msgstr "" "a `header`, that is used by the client to specify optional parameters for " "the request. An empty line is used to mark the end of the header" #: ../../protocols/http.rst:118 #, read-only msgid "an optional MIME document attached to the request" msgstr "an optional MIME document attached to the request" #: ../../protocols/http.rst:120 #, read-only msgid "The response sent by the server also contains three parts :" msgstr "The response sent by the server also contains three parts :" #: ../../protocols/http.rst:122 #, read-only msgid "" "a `status line` , that indicates whether the request was successful or not" msgstr "" "a `status line` , that indicates whether the request was successful or not" #: ../../protocols/http.rst:123 #, read-only msgid "" "a `header`, that contains additional information about the response. The " "response header ends with an empty line." msgstr "" "a `header`, that contains additional information about the response. The " "response header ends with an empty line." #: ../../protocols/http.rst:124 #, read-only msgid "a MIME document" msgstr "a MIME document" #: ../../protocols/http.rst:144 #, read-only msgid "" "Several types of method can be used in HTTP requests. The three most " "important ones are :" msgstr "" "Several types of method can be used in HTTP requests. The three most " "important ones are :" #: ../../protocols/http.rst:146 #, read-only msgid "" "the `GET` method is the most popular one. It is used to retrieve a document " "from a server. The `GET` method is encoded as `GET` followed by the path of " "the URI of the requested document and the version of HTTP used by the " "client. For example, to retrieve the http://www.w3.org/MarkUp/ URI, a client " "must open a TCP connection on port `80` with host `www.w3.org` and send a " "HTTP request containing the following line:" msgstr "" "the `GET` method is the most popular one. It is used to retrieve a document " "from a server. The `GET` method is encoded as `GET` followed by the path of " "the URI of the requested document and the version of HTTP used by the " "client. For example, to retrieve the http://www.w3.org/MarkUp/ URI, a client " "must open a TCP connection on port `80` with host `www.w3.org` and send a " "HTTP request containing the following line:" #: ../../protocols/http.rst:152 #, read-only msgid "" "the `HEAD` method is a variant of the `GET` method that allows the retrieval " "of the header lines for a given URI without retrieving the entire document. " "It can be used by a client to verify if a document exists, for instance." msgstr "" "the `HEAD` method is a variant of the `GET` method that allows the retrieval " "of the header lines for a given URI without retrieving the entire document. " "It can be used by a client to verify if a document exists, for instance." #: ../../protocols/http.rst:153 #, read-only msgid "" "the `POST` method can be used by a client to send a document to a server. " "The document is attached to the HTTP request as a MIME document." msgstr "" "the `POST` method can be used by a client to send a document to a server. " "The document is attached to the HTTP request as a MIME document." #: ../../protocols/http.rst:156 #, read-only msgid "" "HTTP clients and servers can include different HTTP headers in HTTP requests " "and responses. Each HTTP header is encoded as a single ASCII-line terminated " "by `CR` and `LF`. Several of these headers are briefly described below. A " "detailed discussion of the standard headers may be found in :rfc:`1945`. The " "MIME headers can appear in both HTTP requests and HTTP responses." msgstr "" "HTTP clients and servers can include different HTTP headers in HTTP requests " "and responses. Each HTTP header is encoded as a single ASCII-line terminated " "by `CR` and `LF`. Several of these headers are briefly described below. A " "detailed discussion of the standard headers may be found in :rfc:`1945`. The " "MIME headers can appear in both HTTP requests and HTTP responses." #: ../../protocols/http.rst:158 #, read-only msgid "" "the `Content-Length:` header is the :term:`MIME` header that indicates the " "length of the MIME document in bytes." msgstr "" "the `Content-Length:` header is the :term:`MIME` header that indicates the " "length of the MIME document in bytes." #: ../../protocols/http.rst:159 #, read-only msgid "" "the `Content-Type:` header is the :term:`MIME` header that indicates the " "type of the attached MIME document. HTML pages use the `text/html` type." msgstr "" "the `Content-Type:` header is the :term:`MIME` header that indicates the " "type of the attached MIME document. HTML pages use the `text/html` type." #: ../../protocols/http.rst:160 #, read-only msgid "" "the `Content-Encoding:` header indicates how the :term:`MIME document` has " "been encoded. For example, this header would be set to `x-gzip` for a " "document compressed using the gzip_ software." msgstr "" "the `Content-Encoding:` header indicates how the :term:`MIME document` has " "been encoded. For example, this header would be set to `x-gzip` for a " "document compressed using the gzip_ software." #: ../../protocols/http.rst:162 #, read-only msgid "" ":rfc:`1945` and :rfc:`2616` define headers that are specific to HTTP " "responses. These server headers include:" msgstr "" ":rfc:`1945` and :rfc:`2616` define headers that are specific to HTTP " "responses. These server headers include:" #: ../../protocols/http.rst:164 #, read-only msgid "" "the `Server:` header indicates the version of the web server that has " "generated the HTTP response. Some servers provide information about their " "software release and optional modules that they use. For security reasons, " "some system administrators disable these headers to avoid revealing too much " "information about their server to potential attackers." msgstr "" "the `Server:` header indicates the version of the web server that has " "generated the HTTP response. Some servers provide information about their " "software release and optional modules that they use. For security reasons, " "some system administrators disable these headers to avoid revealing too much " "information about their server to potential attackers." #: ../../protocols/http.rst:165 #, read-only msgid "" "the `Date:` header indicates when the HTTP response has been produced by the " "server." msgstr "" "the `Date:` header indicates when the HTTP response has been produced by the " "server." #: ../../protocols/http.rst:166 #, read-only msgid "" "the `Last-Modified:` header indicates the date and time of the last " "modification of the document attached to the HTTP response." msgstr "" "the `Last-Modified:` header indicates the date and time of the last " "modification of the document attached to the HTTP response." #: ../../protocols/http.rst:168 #, read-only msgid "" "Similarly, the following header lines can only appear inside HTTP requests " "sent by a client:" msgstr "" "Similarly, the following header lines can only appear inside HTTP requests " "sent by a client:" #: ../../protocols/http.rst:170 #, read-only msgid "" "the `User-Agent:` header provides information about the client that has " "generated the HTTP request. Some servers analyze this header line and return " "different headers and sometimes different documents for different user " "agents." msgstr "" "the `User-Agent:` header provides information about the client that has " "generated the HTTP request. Some servers analyze this header line and return " "different headers and sometimes different documents for different user " "agents." #: ../../protocols/http.rst:171 #, read-only msgid "" "the `If-Modified-Since:` header is followed by a date. It enables clients to " "cache in memory or on disk recent or most frequently used documents. When a " "client needs to request a URI from a server, it first checks whether the " "document is already in its cache. If it is, the client sends an HTTP request " "with the `If-Modified-Since:` header indicating the date of the cached " "document. The server will only return the document attached to the HTTP " "response if it is newer than the version stored in the client's cache." msgstr "" "the `If-Modified-Since:` header is followed by a date. It enables clients to " "cache in memory or on disk recent or most frequently used documents. When a " "client needs to request a URI from a server, it first checks whether the " "document is already in its cache. If it is, the client sends an HTTP request " "with the `If-Modified-Since:` header indicating the date of the cached " "document. The server will only return the document attached to the HTTP " "response if it is newer than the version stored in the client's cache." #: ../../protocols/http.rst:172 #, read-only msgid "" "the `Referrer:` header is followed by a URI. It indicates the URI of the " "document that the client visited before sending this HTTP request. Thanks to " "this header, the server can know the URI of the document containing the " "hyperlink followed by the client, if any. This information is very useful to " "measure the impact of advertisements containing hyperlinks placed on " "websites." msgstr "" "the `Referrer:` header is followed by a URI. It indicates the URI of the " "document that the client visited before sending this HTTP request. Thanks to " "this header, the server can know the URI of the document containing the " "hyperlink followed by the client, if any. This information is very useful to " "measure the impact of advertisements containing hyperlinks placed on " "websites." #: ../../protocols/http.rst:173 #, read-only msgid "" "the `Host:` header contains the fully qualified domain name of the URI being " "requested." msgstr "" "the `Host:` header contains the fully qualified domain name of the URI being " "requested." #: ../../protocols/http.rst:175 #, read-only msgid "The importance of the `Host:` header line" msgstr "The importance of the `Host:` header line" #: ../../protocols/http.rst:177 #, read-only msgid "" "The first version of HTTP did not include the `Host:` header line. This was " "a severe limitation for web hosting companies. For example consider a web " "hosting company that wants to serve both `web.example.com` and " "`www.example.net` on the same physical server. Both web sites contain a " "`/index.html` document. When a client sends a request for either `http://" "web.example.com/index.html` or `http://www.example.net/index.html`, the HTTP " "1.0 request contains the following line :" msgstr "" "The first version of HTTP did not include the `Host:` header line. This was " "a severe limitation for web hosting companies. For example consider a web " "hosting company that wants to serve both `web.example.com` and " "`www.example.net` on the same physical server. Both web sites contain a " "`/index.html` document. When a client sends a request for either `http://" "web.example.com/index.html` or `http://www.example.net/index.html`, the HTTP " "1.0 request contains the following line :" #: ../../protocols/http.rst:183 #, read-only msgid "" "By parsing this line, a server cannot determine which `index.html` file is " "requested. Thanks to the `Host:` header line, the server knows whether the " "request is for `http://web.example.com/index.html` or `http://www.dummy.net/" "index.html`. Without the `Host:` header, this is impossible. The `Host:` " "header line allowed web hosting companies to develop their business by " "supporting a large number of independent web servers on the same physical " "server." msgstr "" "By parsing this line, a server cannot determine which `index.html` file is " "requested. Thanks to the `Host:` header line, the server knows whether the " "request is for `http://web.example.com/index.html` or `http://www.dummy.net/" "index.html`. Without the `Host:` header, this is impossible. The `Host:` " "header line allowed web hosting companies to develop their business by " "supporting a large number of independent web servers on the same physical " "server." #: ../../protocols/http.rst:185 #, read-only msgid "" "The status line of the HTTP response begins with the version of HTTP used by " "the server (usually `HTTP/1.0` defined in :rfc:`1945` or `HTTP/1.1` defined " "in :rfc:`2616`) followed by a three digit status code and additional " "information in English. HTTP status codes have a similar structure as the " "reply codes used by SMTP:" msgstr "" "The status line of the HTTP response begins with the version of HTTP used by " "the server (usually `HTTP/1.0` defined in :rfc:`1945` or `HTTP/1.1` defined " "in :rfc:`2616`) followed by a three digit status code and additional " "information in English. HTTP status codes have a similar structure as the " "reply codes used by SMTP:" #: ../../protocols/http.rst:187 #, read-only msgid "" "All status codes starting with digit `2` indicate a valid response. `200 Ok` " "indicates that the HTTP request was successfully processed by the server and " "that the response is valid." msgstr "" "All status codes starting with digit `2` indicate a valid response. `200 Ok` " "indicates that the HTTP request was successfully processed by the server and " "that the response is valid." #: ../../protocols/http.rst:188 #, read-only msgid "" "All status codes starting with digit `3` indicate that the requested " "document is no longer available on the server. `301 Moved Permanently` " "indicates that the requested document is no longer available on this server. " "A `Location:` header containing the new URI of the requested document is " "inserted in the HTTP response. `304 Not Modified` is used in response to an " "HTTP request containing the `If-Modified-Since:` header. This status line is " "used by the server if the document stored on the server is not more recent " "than the date indicated in the `If-Modified-Since:` header." msgstr "" "All status codes starting with digit `3` indicate that the requested " "document is no longer available on the server. `301 Moved Permanently` " "indicates that the requested document is no longer available on this server. " "A `Location:` header containing the new URI of the requested document is " "inserted in the HTTP response. `304 Not Modified` is used in response to an " "HTTP request containing the `If-Modified-Since:` header. This status line is " "used by the server if the document stored on the server is not more recent " "than the date indicated in the `If-Modified-Since:` header." #: ../../protocols/http.rst:189 #, read-only msgid "" "All status codes starting with digit `4` indicate that the server has " "detected an error in the HTTP request sent by the client. `400 Bad Request` " "indicates a syntax error in the HTTP request. `404 Not Found` indicates that " "the requested document does not exist on the server." msgstr "" "All status codes starting with digit `4` indicate that the server has " "detected an error in the HTTP request sent by the client. `400 Bad Request` " "indicates a syntax error in the HTTP request. `404 Not Found` indicates that " "the requested document does not exist on the server." #: ../../protocols/http.rst:190 #, read-only msgid "" "All status codes starting with digit `5` indicate an error on the server. `" "500 Internal Server Error` indicates that the server could not process the " "request due to an error on the server itself." msgstr "" "All status codes starting with digit `5` indicate an error on the server. `" "500 Internal Server Error` indicates that the server could not process the " "request due to an error on the server itself." #: ../../protocols/http.rst:192 #, read-only msgid "" "In both HTTP requests and responses, the MIME document refers to a " "representation of the document with the MIME headers indicating the type of " "document and its size." msgstr "" "In both HTTP requests and responses, the MIME document refers to a " "representation of the document with the MIME headers indicating the type of " "document and its size." #: ../../protocols/http.rst:194 #, read-only msgid "" "As an illustration of HTTP/1.0, the transcript below shows a HTTP request " "for `http://www.ietf.org `_ and the corresponding HTTP " "response. The HTTP request was sent using the curl_ command line tool. The " "`User-Agent:` header line contains more information about this client " "software. There is no MIME document attached to this HTTP request, and it " "ends with a blank line." msgstr "" "As an illustration of HTTP/1.0, the transcript below shows a HTTP request " "for `http://www.ietf.org `_ and the corresponding HTTP " "response. The HTTP request was sent using the curl_ command line tool. The " "`User-Agent:` header line contains more information about this client " "software. There is no MIME document attached to this HTTP request, and it " "ends with a blank line." #: ../../protocols/http.rst:203 #, read-only msgid "" "The HTTP response indicates the version of the server software used with the " "modules included. The `Last-Modified:` header indicates that the requested " "document was modified about one week before the request. A HTML document " "(not shown) is attached to the response. Note the blank line between the " "header of the HTTP response and the attached MIME document. The `Server:` " "header line has been truncated in this output." msgstr "" "The HTTP response indicates the version of the server software used with the " "modules included. The `Last-Modified:` header indicates that the requested " "document was modified about one week before the request. A HTML document " "(not shown) is attached to the response. Note the blank line between the " "header of the HTTP response and the attached MIME document. The `Server:` " "header line has been truncated in this output." #: ../../protocols/http.rst:216 #, read-only msgid "" "HTTP was initially designed to share text documents. For this reason, and to " "ease the implementation of clients and servers, the designers of HTTP chose " "to open a TCP connection for each HTTP request. This implies that a client " "must open one TCP connection for each URI that it wants to retrieve from a " "server as illustrated on the figure below, showing HTTP 1.0 and the " "underlying TCP connection. For a web page containing only text documents " "this was a reasonable design choice as the client usually remains idle while " "the (human) user is reading the retrieved document." msgstr "" "HTTP was initially designed to share text documents. For this reason, and to " "ease the implementation of clients and servers, the designers of HTTP chose " "to open a TCP connection for each HTTP request. This implies that a client " "must open one TCP connection for each URI that it wants to retrieve from a " "server as illustrated on the figure below, showing HTTP 1.0 and the " "underlying TCP connection. For a web page containing only text documents " "this was a reasonable design choice as the client usually remains idle while " "the (human) user is reading the retrieved document." #: ../../protocols/http.rst:252 #, read-only msgid "" "However, as the web evolved to support richer documents containing images, " "opening a TCP connection for each URI became a performance problem " "[Mogul1995]_. Indeed, besides its HTML part, a web page may include dozens " "of images or more. Forcing the client to open a TCP connection for each " "component of a web page has two important drawbacks. First, the client and " "the server must exchange packets to open and close a TCP connection as we " "will see later. This increases the network overhead and the total delay of " "completely retrieving all the components of a web page. Second, a large " "number of established TCP connections may be a performance bottleneck on " "servers." msgstr "" "However, as the web evolved to support richer documents containing images, " "opening a TCP connection for each URI became a performance problem " "[Mogul1995]_. Indeed, besides its HTML part, a web page may include dozens " "of images or more. Forcing the client to open a TCP connection for each " "component of a web page has two important drawbacks. First, the client and " "the server must exchange packets to open and close a TCP connection as we " "will see later. This increases the network overhead and the total delay of " "completely retrieving all the components of a web page. Second, a large " "number of established TCP connections may be a performance bottleneck on " "servers." #: ../../protocols/http.rst:255 #, read-only msgid "" "This problem was solved by extending HTTP to support persistent TCP " "connections :rfc:`2616`. A persistent connection is a TCP connection over " "which a client may send several HTTP requests. This is illustrated in the " "figure below showing the persistent connection of HTTP 1.1." msgstr "" "This problem was solved by extending HTTP to support persistent TCP " "connections :rfc:`2616`. A persistent connection is a TCP connection over " "which a client may send several HTTP requests. This is illustrated in the " "figure below showing the persistent connection of HTTP 1.1." #: ../../protocols/http.rst:306 #, read-only msgid "" "To allow the clients and servers to control the utilization of these " "persistent TCP connections, HTTP 1.1 :rfc:`2616` defines several new HTTP " "headers:" msgstr "" "To allow the clients and servers to control the utilization of these " "persistent TCP connections, HTTP 1.1 :rfc:`2616` defines several new HTTP " "headers:" #: ../../protocols/http.rst:308 #, read-only msgid "" "The `Connection:` header is used with the `Keep-Alive` argument by the " "client to indicate that it expects the underlying TCP connection to be " "persistent. When this header is used with the `Close` argument, it indicates " "that the entity that sent it will close the underlying TCP connection at the " "end of the HTTP response." msgstr "" "The `Connection:` header is used with the `Keep-Alive` argument by the " "client to indicate that it expects the underlying TCP connection to be " "persistent. When this header is used with the `Close` argument, it indicates " "that the entity that sent it will close the underlying TCP connection at the " "end of the HTTP response." #: ../../protocols/http.rst:309 #, read-only msgid "" "The `Keep-Alive:` header is used by the server to inform the client about " "how it agrees to use the persistent connection. A typical `Keep-Alive:` " "contains two parameters: the maximum number of requests that the server " "agrees to serve on the underlying TCP connection and the timeout (in seconds)" " after which the server will close an idle connection" msgstr "" "The `Keep-Alive:` header is used by the server to inform the client about " "how it agrees to use the persistent connection. A typical `Keep-Alive:` " "contains two parameters: the maximum number of requests that the server " "agrees to serve on the underlying TCP connection and the timeout (in seconds)" " after which the server will close an idle connection" #: ../../protocols/http.rst:311 #, read-only msgid "" "The example below shows the operation of HTTP/1.1 over a persistent TCP " "connection to retrieve three URIs stored on the same server. Once the " "connection has been established, the client sends its first request with the " "`Connection: Keep-Alive` header to request a persistent connection." msgstr "" "The example below shows the operation of HTTP/1.1 over a persistent TCP " "connection to retrieve three URIs stored on the same server. Once the " "connection has been established, the client sends its first request with the " "`Connection: Keep-Alive` header to request a persistent connection." #: ../../protocols/http.rst:321 #, read-only msgid "" "The server replies with the `Connection: Keep-Alive` header and indicates " "that it accepts a maximum of 100 HTTP requests over this connection and that " "it will close the connection if it remains idle for 15 seconds." msgstr "" "The server replies with the `Connection: Keep-Alive` header and indicates " "that it accepts a maximum of 100 HTTP requests over this connection and that " "it will close the connection if it remains idle for 15 seconds." #: ../../protocols/http.rst:336 #, read-only msgid "" "The client sends a second request for the style sheet of the retrieved web " "page." msgstr "" "The client sends a second request for the style sheet of the retrieved web " "page." #: ../../protocols/http.rst:347 #, read-only msgid "" "The server replies with the requested style sheet and maintains the " "persistent connection. Note that the server only accepts 99 remaining HTTP " "requests over this persistent connection." msgstr "" "The server replies with the requested style sheet and maintains the " "persistent connection. Note that the server only accepts 99 remaining HTTP " "requests over this persistent connection." #: ../../protocols/http.rst:362 #, read-only msgid "" "Then the client requested the web server's icon [#ffavicon]_. This server " "does not contain such an icon and thus replies with a `404` HTTP status. " "However, the underlying TCP connection is not closed immediately." msgstr "" "Then the client requested the web server's icon [#ffavicon]_. This server " "does not contain such an icon and thus replies with a `404` HTTP status. " "However, the underlying TCP connection is not closed immediately." #: ../../protocols/http.rst:383 #, read-only msgid "" "As illustrated above, a client can send several HTTP requests over the same " "persistent TCP connection. However, it is important to note that all of " "these HTTP requests are considered to be independent by the server. Each " "HTTP request must be self-contained. This implies that each request must " "include all the header lines that are required by the server to understand " "the request. The independence of these requests is one of the key design " "choices of HTTP. As a consequence of this design choice, when a server " "processes a HTTP request, it does not use any other information than what is " "contained in the request itself. This explains why the client adds its `User-" "Agent:` header in all of the HTTP requests that it sends over the persistent " "TCP connection." msgstr "" "As illustrated above, a client can send several HTTP requests over the same " "persistent TCP connection. However, it is important to note that all of " "these HTTP requests are considered to be independent by the server. Each " "HTTP request must be self-contained. This implies that each request must " "include all the header lines that are required by the server to understand " "the request. The independence of these requests is one of the key design " "choices of HTTP. As a consequence of this design choice, when a server " "processes a HTTP request, it does not use any other information than what is " "contained in the request itself. This explains why the client adds its `User-" "Agent:` header in all of the HTTP requests that it sends over the persistent " "TCP connection." #: ../../protocols/http.rst:385 #, read-only msgid "" "However, in practice, some servers want to provide content tuned for each " "user. For example, some servers can provide information in several " "languages. Other servers want to provide advertisements that are targeted to " "different types of users. To do this, servers need to maintain some " "information about the preferences of each user and use this information to " "produce content matching the user's preferences. HTTP contains several " "mechanisms to solve this problem. We discuss three of them below." msgstr "" "However, in practice, some servers want to provide content tuned for each " "user. For example, some servers can provide information in several " "languages. Other servers want to provide advertisements that are targeted to " "different types of users. To do this, servers need to maintain some " "information about the preferences of each user and use this information to " "produce content matching the user's preferences. HTTP contains several " "mechanisms to solve this problem. We discuss three of them below." #: ../../protocols/http.rst:387 #, read-only msgid "" "A first solution is to force the users to be authenticated. This was the " "solution used by `FTP` to control the files that each user could access. " "Initially, user names and passwords could be included inside URIs :rfc:`1738`" ". However, placing passwords in the clear in a potentially publicly visible " "URI is completely insecure and this usage has now been deprecated :rfc:`3986`" ". HTTP supports several extension headers :rfc:`2617` that can be used by a " "server to request the authentication of the client by providing his/her " "credentials. However, user names and passwords have not been popular on web " "servers as they force human users to remember one user name and one password " "per server. Remembering a password is acceptable when a user needs to access " "protected content, but users will not accept to remember a unique user name " "and password for each web sites that they visit." msgstr "" "A first solution is to force the users to be authenticated. This was the " "solution used by `FTP` to control the files that each user could access. " "Initially, user names and passwords could be included inside URIs :rfc:`1738`" ". However, placing passwords in the clear in a potentially publicly visible " "URI is completely insecure and this usage has now been deprecated :rfc:`3986`" ". HTTP supports several extension headers :rfc:`2617` that can be used by a " "server to request the authentication of the client by providing his/her " "credentials. However, user names and passwords have not been popular on web " "servers as they force human users to remember one user name and one password " "per server. Remembering a password is acceptable when a user needs to access " "protected content, but users will not accept to remember a unique user name " "and password for each web sites that they visit." #: ../../protocols/http.rst:389 #, read-only msgid "" "A second solution to allow servers to tune that content to the needs and " "capabilities of the user is to rely on the different types of `Accept-*` " "HTTP headers. For example, the `Accept-Language:` header can be used by the " "client to indicate its preferred languages. Unfortunately, in practice this " "header is usually set based on the default language of the browser and it is " "difficult for a user to indicate the language it prefers by selecting " "options for each visited web server." msgstr "" "A second solution to allow servers to tune that content to the needs and " "capabilities of the user is to rely on the different types of `Accept-*` " "HTTP headers. For example, the `Accept-Language:` header can be used by the " "client to indicate its preferred languages. Unfortunately, in practice this " "header is usually set based on the default language of the browser and it is " "difficult for a user to indicate the language it prefers by selecting " "options for each visited web server." #: ../../protocols/http.rst:391 #, read-only msgid "" "The third and widely adopted solution are HTTP cookies. HTTP cookies were " "initially developed as a private extension by Netscape_. They are now part " "of the standard :rfc:`6265`. In a nutshell, a cookie is a short string that " "is chosen by a server to represent a given client. Two HTTP headers are used " ": `Cookie:` and `Set-Cookie:`. When a server receives an HTTP request from a " "new client (i.e. an HTTP request that does not contain the `Cookie:` header)" ", it generates a cookie for the client and includes it in the `Set-Cookie:` " "header of the returned HTTP response. The `Set-Cookie:` header contains " "several additional parameters including the domain names for which the " "cookie is valid. The client stores all received cookies on disk and every " "time it sends an HTTP request, it verifies whether it already knows a cookie " "for this domain. If so, it attaches the `Cookie:` header to the HTTP " "request. This is illustrated in the figure below with HTTP 1.1, but cookies " "also work with HTTP 1.0." msgstr "" "The third and widely adopted solution are HTTP cookies. HTTP cookies were " "initially developed as a private extension by Netscape_. They are now part " "of the standard :rfc:`6265`. In a nutshell, a cookie is a short string that " "is chosen by a server to represent a given client. Two HTTP headers are used " ": `Cookie:` and `Set-Cookie:`. When a server receives an HTTP request from a " "new client (i.e. an HTTP request that does not contain the `Cookie:` header)" ", it generates a cookie for the client and includes it in the `Set-Cookie:` " "header of the returned HTTP response. The `Set-Cookie:` header contains " "several additional parameters including the domain names for which the " "cookie is valid. The client stores all received cookies on disk and every " "time it sends an HTTP request, it verifies whether it already knows a cookie " "for this domain. If so, it attaches the `Cookie:` header to the HTTP " "request. This is illustrated in the figure below with HTTP 1.1, but cookies " "also work with HTTP 1.0." #: ../../protocols/http.rst:438 #, read-only msgid "Privacy issues with HTTP cookies" msgstr "Privacy issues with HTTP cookies" #: ../../protocols/http.rst:440 #, read-only msgid "" "The HTTP cookies introduced by Netscape_ are key for large e-commerce " "websites. However, they have also raised many discussions concerning their `" "potential misuses `" "_. Consider `ad.com`, a company that delivers lots of advertisements on web " "sites. A web site that wishes to include `ad.com`'s advertisements next to " "its content will add links to `ad.com` inside its HTML pages. If `ad.com` is " "used by many web sites, `ad.com` could be able to track the interests of all " "the users that visit its client websites and use this information to provide " "targeted advertisements. Privacy advocates have even `sued `_ online advertisement companies to force them to " "comply with the privacy regulations. More recent related technologies also " "raise `privacy concerns `_." msgstr "" "The HTTP cookies introduced by Netscape_ are key for large e-commerce " "websites. However, they have also raised many discussions concerning their `" "potential misuses `" "_. Consider `ad.com`, a company that delivers lots of advertisements on web " "sites. A web site that wishes to include `ad.com`'s advertisements next to " "its content will add links to `ad.com` inside its HTML pages. If `ad.com` is " "used by many web sites, `ad.com` could be able to track the interests of all " "the users that visit its client websites and use this information to provide " "targeted advertisements. Privacy advocates have even `sued `_ online advertisement companies to force them to " "comply with the privacy regulations. More recent related technologies also " "raise `privacy concerns `_." #: ../../protocols/http.rst:443 #, read-only msgid "Footnotes" msgstr "Footnotes" #: ../../protocols/http.rst:444 #, read-only msgid "" "An example of a non-retrievable URI is `urn:isbn:0-380-81593-1` which is an " "unique identifier for a book, through the urn scheme (see :rfc:`3187`). Of " "course, any URI can be made retrievable via a dedicated server or a new " "protocol but this one has no explicit protocol. Same thing for the scheme " "tag (see :rfc:`4151`), often used in Web syndication " "(see :rfc:`4287` about the Atom syndication format). Even when the scheme is " "retrievable (for instance with `http`), it is often used only as an " "identifier, not as a way to get a resource. See http://norman.walsh.name/" "2006/07/25/namesAndAddresses for a good explanation." msgstr "" "An example of a non-retrievable URI is `urn:isbn:0-380-81593-1` which is an " "unique identifier for a book, through the urn scheme (see :rfc:`3187`). Of " "course, any URI can be made retrievable via a dedicated server or a new " "protocol but this one has no explicit protocol. Same thing for the scheme " "tag (see :rfc:`4151`), often used in Web syndication " "(see :rfc:`4287` about the Atom syndication format). Even when the scheme is " "retrievable (for instance with `http`), it is often used only as an " "identifier, not as a way to get a resource. See http://norman.walsh.name/" "2006/07/25/namesAndAddresses for a good explanation." #: ../../protocols/http.rst:447 #, read-only msgid "" "The list of standard URI schemes is maintained by IANA_ at http://" "www.iana.org/assignments/uri-schemes.html" msgstr "" "The list of standard URI schemes is maintained by IANA_ at http://" "www.iana.org/assignments/uri-schemes.html" #: ../../protocols/http.rst:449 #, read-only msgid "" "Favorite icons are small icons that are used to represent web servers in the " "toolbar of Internet browsers. Microsoft added this feature in their browsers " "without taking into account the W3C standards. See http://www.w3.org/2005/10/" "howto-favicon for a discussion on how to cleanly support such favorite icons." msgstr "" "Favorite icons are small icons that are used to represent web servers in the " "toolbar of Internet browsers. Microsoft added this feature in their browsers " "without taking into account the W3C standards. See http://www.w3.org/2005/10/" "howto-favicon for a discussion on how to cleanly support such favorite icons."