path: root/lib/inets/doc/src/httpc.xml

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<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2004</year><year>2017</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>httpc</title>
    <prepared>Ingela Anderton Andin</prepared>
    <responsible></responsible>
    <docno></docno>
    <date></date>
    <rev></rev>
  </header>

  <module>httpc</module>
  <modulesummary>An HTTP/1.1 client</modulesummary>

  <description>
    <p>This module provides the API to an HTTP/1.1 compatible client according 
      to <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>. 
    Caching is not supported.</p>
    <note>
      <p>When starting the <c>Inets</c> application, a manager process for the
	default profile is started. The functions in this API
	that do not explicitly use a profile accesses the
	default profile. A profile keeps track of proxy options,
	cookies, and other options that can be applied to more than one
	request.</p>

	<p>If the scheme <c>https</c> is used, the <c>SSL</c> application must
	be started. When <c>https</c> links need to go through a proxy, the
	CONNECT method extension to HTTP-1.1 is used to establish a
	tunnel and then the connection is upgraded to TLS.
	However, "TLS upgrade" according to <url href="http://www.ietf.org/rfc/rfc2817.txt">RFC 2817</url>is not
	supported.</p>

      <p>Pipelining is only used if the pipeline
      time-out is set, otherwise persistent connections without
      pipelining are used. That is, the client always waits for
      the previous response before sending the next request.</p>
    </note>
    <p>Some examples are provided in the <seealso
    marker="http_client">Inets User's Guide</seealso>.</p>
  </description>
  
  <section>
    <title>DATA TYPES</title>
    <marker id="DATA_TYPES"></marker>
    <p>Type definitions that are used more than once in
      this module:</p>
    <p><c>boolean() = true | false</c></p>
    <p><c>string()</c> = list of ASCII characters</p>
    <p><c>request_id() = reference()</c></p>
    <p><c>profile() = atom()</c></p>
    <p><c>path() = string()</c> representing a file path or directory path</p>
    <p><c>ip_address()</c> = See the
    <seealso marker="kernel:inet">inet(3)</seealso> manual page in Kernel.</p>
    <p><c>socket_opt()</c> = See the options used by
    <seealso marker="kernel:gen_tcp">gen_tcp(3)</seealso> <c>gen_tcp(3)</c> and 
    <seealso marker="ssl:ssl">ssl(3)</seealso> connect(s)</p>
  
  </section>
  
  <section>
    <title>HTTP DATA TYPES</title>
    <p>Type definitions related to HTTP:</p>

    <p><c>method() = head | get | put | post | trace | options | delete | patch</c></p>
    <taglist>
      <tag><c>request()</c></tag>
      <item><p>= <c>{url(), headers()}</c></p>
      <p>| <c>{url(), headers(), content_type(), body()}</c></p>
      </item>
    </taglist>
    <p><c>url() = string()</c> syntax according to the URI definition in
    <url href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</url>, 
    for example <c>"http://www.erlang.org"</c></p>
    <p><c>status_line() = {http_version(), status_code(), reason_phrase()}</c></p>
    <p><c>http_version() = string()</c>, for example, <c>"HTTP/1.1"</c></p>
    <p><c>status_code() = integer()</c></p>
    <p><c>reason_phrase() = string()</c></p>
    <p><c>content_type() = string()</c></p>
    <p><c>headers() = [header()]</c></p>
    <p><c>header() = {field(), value()}</c></p>
    <p><c>field() = string()</c></p>
    <p><c>value() = string()</c></p>
    <taglist>
      <tag><c>body()</c></tag>
      <item><p>= <c>string() | binary()</c></p>
      <p>| <c>{fun(accumulator())</c></p>
      <p><c> -> body_processing_result(), accumulator()}</c></p>
      <p>| <c>{chunkify, fun(accumulator())</c></p>
      <p><c> -> body_processing_result(), accumulator()}</c></p>
      </item>
    </taglist>
    <p><c>body_processing_result() = eof | {ok, iolist(), accumulator()}</c></p>
    <p><c>accumulator() = term()</c></p>
    <p><c>filename() = string()</c></p>
 <p>For more information about HTTP, see
 <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>.</p> 
</section>
  
  <section>
    <title>SSL DATA TYPES</title>
    <p>See <seealso marker="ssl:ssl">ssl(3)</seealso> for information
    about <c>SSL</c> options (<c>ssloptions()</c>). </p>
  </section>

  <section>
    <title>HTTP CLIENT SERVICE START/STOP</title>
    
    <p>An HTTP client can be configured to start when starting the <c>Inets</c>
      application or started dynamically in runtime by calling the
      <c>Inets</c> application API <c>inets:start(httpc, ServiceConfig)</c>
      or <c>inets:start(httpc,  ServiceConfig, How)</c>,
      see <seealso marker="inets">inets(3)</seealso>.
      The configuration options are as follows:</p>
    <taglist>
      <tag>{profile, profile()}</tag>
      <item><p>Name of the profile, see
	<seealso marker="#DATA_TYPES">DATA TYPES</seealso>.
      This option is mandatory.</p></item>
      <tag>{data_dir, path()}</tag>
      <item><p>Directory where the profile
	can save persistent data. If omitted, all cookies are treated
	as session cookies.</p></item>
    </taglist>

    <p>The client can be stopped using <c>inets:stop(httpc, Pid)</c> or
    <c>inets:stop(httpc, Profile)</c>.</p>
  </section>
  
  <funcs>
   
    <func>
      <name>cancel_request(RequestId) -></name>
      <name>cancel_request(RequestId, Profile) -> ok</name>
      <fsummary>Cancels an asynchronous HTTP request.</fsummary>
      <type>
        <v>RequestId = request_id() - A unique identifier as returned
        by request/4</v>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
      </type>
      <desc>
        <p>Cancels an asynchronous HTTP request. Notice that this does not guarantee
	that the request response is not delivered. Because it is asynchronous,
	the request can already have been completed when the cancellation arrives.
	</p>
      </desc>
    </func>

    <func>
      <name>cookie_header(Url) -> </name>
      <name>cookie_header(Url, Profile | Opts) -> header() | {error, Reason}</name>
      <name>cookie_header(Url, Opts, Profile) -> header() | {error, Reason}</name>
      <fsummary>Returns the cookie header that would have been sent when
      making a request to URL using the profile <c>Profile</c>.</fsummary>
      <type>
        <v>Url = url()</v>
        <v>Opts = [cookie_header_opt()]</v>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c>.</d>
        <v>cookie_header_opt() = {ipv6_host_with_brackets, boolean()}</v>
      </type>
      <desc>
        <p>Returns the cookie header that would have been sent
	when making a request to <c>Url</c> using profile <c>Profile</c>.
	If no profile is specified, the default profile is used.</p>
	<p>Option <c>ipv6_host_with_bracket</c> deals with how to 
	parse IPv6 addresses. For details,
	see argument <c>Options</c> of
	<seealso marker="#request-4">request/[4,5]</seealso>.</p>
      </desc>
    </func>

     <func>
      <name>get_options(OptionItems) -> {ok, Values} | {error, Reason}</name>
      <name>get_options(OptionItems, Profile) -> {ok, Values} | {error, Reason}</name>
      <fsummary>Gets the currently used options.</fsummary>
      <type>
        <v>OptionItems = all | [option_item()]</v>
	<v>option_item() = proxy |
	                   https_proxy |
                           max_sessions | 
			   keep_alive_timeout | 
	                   max_keep_alive_length | 
			   pipeline_timeout | 
			   max_pipeline_length | 
			   cookies | 
			   ipfamily | 
			   ip | 
			   port | 
			   socket_opts | 
	                   verbose |
	                   unix_socket</v>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can used.</d>
        <v>Values = [{option_item(), term()}]</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Retrieves the options currently used by the client.</p>
      </desc>
    </func>

    <func>
      <name>info() -> list()</name>
      <name>info(Profile) -> list()</name>
      <fsummary>Produces a list of miscellaneous information.</fsummary>
      <type>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
      </type>
      <desc>
        <p>Produces a list of miscellaneous information. 
	Intended for debugging. 
	If no profile is specified, the default profile is used.</p>
      </desc>
    </func>

    
    <func>
      <name>reset_cookies() -> void()</name>
      <name>reset_cookies(Profile) -> void()</name>
      <fsummary>Resets the cookie database.</fsummary>
      <type>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
      </type>
      <desc>
        <p>Resets (clears) the cookie database for the specified 
	<c>Profile</c>. If no profile is specified the default profile 
	is used.</p>
      </desc>
    </func>
    
    <func>
      <name>request(Url) -> </name>
      <name>request(Url, Profile) -> {ok, Result} | {error, Reason}</name>
      <fsummary>Sends a get HTTP request.</fsummary>
      <type>
        <v>Url = url()</v> 
	<v>Result = {status_line(), headers(), Body} | 
                    {status_code(), Body} | request_id()</v>
	<v>Body = string() | binary()</v>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
	<v>Reason = term()</v>
      </type>
      <desc>
        <p>Equivalent to <c>httpc:request(get, {Url, []}, [], [])</c>.</p>
      </desc>
    </func>

    <func>
      <name>request(Method, Request, HTTPOptions, Options) -></name>
      <name>request(Method, Request, HTTPOptions, Options, Profile) -> {ok, Result} | {ok, saved_to_file} | {error, Reason}</name>
      
      <fsummary>Sends an HTTP request.</fsummary>
      <type>
        <v>Method = method()</v>
        <v>Request = request()</v>
        <v>HTTPOptions = http_options()</v>
        <v>http_options() = [http_option()]</v>
        <v>http_option() = {timeout,         timeout()} | 
                           {connect_timeout, timeout()} | 
                           {ssl,             ssloptions()} | 
                           {essl,            ssloptions()} | 
                           {autoredirect,    boolean()} | 
                           {proxy_auth, {userstring(), passwordstring()}} | 
                           {version,         http_version()} | 
                           {relaxed,         boolean()}</v>
        <v>timeout() = integer() >= 0 | infinity</v>
        <v>Options = options()</v>
        <v>options() = [option()]</v>
        <v>option() = {sync,                    boolean()} | 
                      {stream,                  stream_to()} | 
                      {body_format,             body_format()} | 
                      {full_result,             boolean()} | 
                      {headers_as_is,           boolean() |
                      {socket_opts,             socket_opts()} | 
                      {receiver,                receiver()} |
	              {ipv6_host_with_brackets, boolean()}</v>
        <v>stream_to() = none | self | {self, once} | filename()</v>
        <v>socket_opts() = [socket_opt()]</v>
        <v>receiver() = pid() | function()/1 | {Module, Function, Args}</v>
        <v>Module = atom()</v>
        <v>Function = atom()</v>
        <v>Args = list()</v>
	<v>body_format() = string | binary</v>
        <v>Result = {status_line(), headers(), Body} | 
                    {status_code(), Body} | request_id()</v>
        <v>Body = string() | binary()</v>
        <v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
        <v>Reason = term()</v>
      </type>

      <desc>
        <p>Sends an HTTP request. The function can be both synchronous
	and asynchronous. In the latter case, the function returns
	<c>{ok, RequestId}</c> and then the information is delivered
	to the <c>receiver</c> depending on that value.</p>

        <p>HTTP option (<c>http_option()</c>) details:</p>
        <marker id="request2_http_options"></marker>
        <taglist>
          <tag><c><![CDATA[timeout]]></c></tag>
          <item>
            <p>Time-out time for the request.</p>
            <p>The clock starts ticking when the request is sent.</p>
            <p>Time is in milliseconds.</p>
            <p>Default is <c>infinity</c>.</p>
	  </item>

          <tag><c><![CDATA[connect_timeout]]></c></tag>
          <item>
            <p>Connection time-out time, used during the initial request, 
	    when the client is <em>connecting</em> to the server.</p>
            <p>Time is in milliseconds.</p>
            <p>Default is the value of option <c>timeout</c>.</p>
	  </item>

          <tag><c><![CDATA[ssl]]></c></tag>
          <item>
            <p>This is the <c>SSL/TLS</c> connectin configuration option.</p>
            <p>Defaults to <c>[]</c>. See <seealso marker="ssl:ssl">ssl:connect/[2,3,4]</seealso>  for available options.</p>
	  </item>

          <tag><c><![CDATA[autoredirect]]></c></tag>
          <item>
	    <p>The client automatically retrieves the information
	    from the new URI and returns that as the result, instead 
	    of a 30X-result code.</p>
	    <p>For some 30X-result codes, automatic redirect 
	    is not allowed. In these cases the 30X-result is always
	    returned.</p>
	    <p>Default is <c>true</c>.</p>
	  </item>

          <tag><c><![CDATA[proxy_auth]]></c></tag>
          <item>
            <p>A proxy-authorization header using the provided username and 
	    password is added to the request.</p>
	  </item>

          <tag><c><![CDATA[version]]></c></tag>
          <item>
            <p>Can be used to make the client act as an <c>HTTP/1.0</c> or
	    <c>HTTP/0.9</c> client. By default this is an <c>HTTP/1.1</c> 
	    client. When using <c>HTTP/1.0</c> persistent connections are 
	    not used.</p>
	    <p>Default is the string <c>"HTTP/1.1"</c>.</p>
	  </item>

          <tag><c><![CDATA[relaxed]]></c></tag>
          <item>
            <p>If set to <c>true</c>, workarounds for known server deviations 
	    from the HTTP-standard are enabled.</p>
            <p>Default is <c>false</c>.</p>
	  </item>
        </taglist>

        <p>Option (<c>option()</c>) details:</p>
        <taglist>
          <tag><c><![CDATA[sync]]></c></tag>
          <item>
            <p>Option for the request to be synchronous or asynchronous.</p>
            <p>Default is <c>true</c>.</p>
	  </item>

          <tag><c><![CDATA[stream]]></c></tag>
          <item>
            <p>Streams the body of a 200 or 206 response to the calling 
	    process or to a file. When streaming to the calling process 
	    using option <c>self</c>, the following stream messages
	    are sent to that process: <c>{http, {RequestId,
	    stream_start, Headers}}, {http, {RequestId, stream,
	    BinBodyPart}}, and {http, {RequestId, stream_end, Headers}}</c>.</p>
	    <p>When streaming to the calling processes using option
	    <c>{self, once}</c>, the first message has an extra
	    element, that is, <c>{http, {RequestId, stream_start, Headers, Pid}}</c>.
	    This is the process id to be used as an argument to
	    <c>httpc:stream_next/1</c> to trigger the next message to be sent to
	    the calling process.</p>
	    <p>Notice that chunked encoding can add
	    headers so that there are more headers in the <c>stream_end</c>
	    message than in <c>stream_start</c>.
	    When streaming to a file and the request is asynchronous, the
	    message <c>{http, {RequestId, saved_to_file}}</c> is sent.</p>
            <p>Default is <c>none</c>.</p>
	  </item>

          <tag><c><![CDATA[body_format]]></c></tag>
          <item>
            <p>Defines if the body is to be delivered as a string or 
	    binary. This option is only valid for the synchronous 
	    request.</p>
            <p>Default is <c>string</c>.</p>
	  </item>

          <tag><c><![CDATA[full_result]]></c></tag>
          <item>
            <p>Defines if a "full result" is to be returned to the caller (that is,
	    the body, the headers, and the entire status line) or not 
	    (the body and the status code).</p>
            <p>Default is <c>true</c>.</p>
	  </item>

          <tag><c><![CDATA[headers_as_is]]></c></tag>
          <item>
            <p>Defines if the headers provided by the user are to be made 
	    lower case or to be regarded as case sensitive.</p>
            <p>The HTTP standard requires them to be 
	    case insensitive. Use this feature only if there is 
	    no other way to communicate with the server or for testing 
	    purpose. When this option is used, no headers 
	    are automatically added. All necessary headers must be
	    provided by the user.</p>
	    <p>Default is <c>false</c>.</p>
	  </item>

          <tag><c><![CDATA[socket_opts]]></c></tag>
          <item>
            <p>Socket options to be used for this and subsequent 
	    requests.</p>
	    <p>Overrides any value set by function
	    <seealso marker="#set_options-1">set_options</seealso>.</p>
            <p>The validity of the options is <em>not</em> checked by
            the HTTP client they are assumed to be correct and passed
            on to ssl application and inet driver, which may reject
            them if they are not correct. Note that the current
            implementation assumes the requests to the same host, port
            combination will use the same socket options.
	    </p>
	    
            <p>By default the socket options set by function
	    <seealso marker="#set_options-1">set_options/[1,2]</seealso> 
	     are used when establishing a connection.</p>
	  </item>

          <tag><c><![CDATA[receiver]]></c></tag>
          <item>
            <p>Defines how the client delivers the result of an
	    asynchronous request (<c>sync</c> has the value 
	    <c>false</c>).</p>

            <taglist>
              <tag><c><![CDATA[pid()]]></c></tag>
              <item>
	        <p>Messages are sent to this process in the format 
		<c>{http, ReplyInfo}</c>.</p>
	      </item>

              <tag><c><![CDATA[function/1]]></c></tag>
              <item>
	        <p>Information is delivered to the receiver through calls 
		to the provided fun <c>Receiver(ReplyInfo)</c>.</p>
  	      </item>

              <tag><c><![CDATA[{Module, Function, Args}]]></c></tag>
              <item>
	        <p>Information is delivered to the receiver through calls 
		to the callback function 
		<c>apply(Module, Function, [ReplyInfo | Args])</c>.</p>
	      </item>
            </taglist>
            <p>In all of these cases, <c>ReplyInfo</c> has the following
              structure:</p>

<pre>
{RequestId, saved_to_file}
{RequestId, {error, Reason}}
{RequestId, Result}
{RequestId, stream_start, Headers}
{RequestId, stream_start, Headers, HandlerPid}
{RequestId, stream, BinBodyPart}
{RequestId, stream_end, Headers}</pre>

            <p>Default is the <c>pid</c> of the process calling the request 
	    function (<c>self()</c>). </p>

	    <marker id="ipv6_host_with_brackets"></marker>
	  </item>

          <tag><c><![CDATA[ipv6_host_with_brackets]]></c></tag>
          <item>
            <p>Defines when parsing the Host-Port part of an URI with an IPv6 address 
	    with brackets, if those brackets are to be retained (<c>true</c>) 
	    or stripped (<c>false</c>).</p>
            <p>Default is <c>false</c>.</p>
	  </item>

        </taglist>
      </desc>
    </func>

  
    <func>
      <name>set_options(Options) -> </name>
      <name>set_options(Options, Profile) -> ok | {error, Reason}</name>
      <fsummary>Sets options to be used for subsequent requests.</fsummary>
      <type>
        <v>Options = [Option]</v>
        <v>Option = {proxy, {Proxy, NoProxy}}</v>
	<v>| {https_proxy, {Proxy, NoProxy}}</v>
	<v>| {max_sessions, MaxSessions}</v>
	<v>| {max_keep_alive_length, MaxKeepAlive}</v>
	<v>| {keep_alive_timeout, KeepAliveTimeout}</v>
	<v>| {max_pipeline_length, MaxPipeline}</v>
	<v>| {pipeline_timeout, PipelineTimeout}</v>
	<v>| {cookies, CookieMode}</v>
	<v>| {ipfamily, IpFamily}</v>
	<v>| {ip, IpAddress}</v>
	<v>| {port, Port}</v>
	<v>| {socket_opts, socket_opts()}</v>
	<v>| {verbose, VerboseMode}</v>
	<v>| {unix_socket, UnixSocket}</v>
        <v>Proxy = {Hostname, Port}</v>
        <v>Hostname = string()</v>
        <d>Example: "localhost" or "foo.bar.se"</d>
        <v>Port = integer()</v>
        <d>Example: 8080</d>
        <v>NoProxy = [NoProxyDesc]</v>
        <v>NoProxyDesc = DomainDesc | HostName | IPDesc</v>
        <v>DomainDesc = "*.Domain"</v>
        <d>Example: "*.ericsson.se"</d>
        <v>IpDesc = string()</v>
        <d>Example: "134.138" or "[FEDC:BA98" 
	(all IP addresses starting with 134.138 or FEDC:BA98), 
	"66.35.250.150" or "[2010:836B:4179::836B:4179]" (a complete IP address). 
	<c>proxy</c> defaults to <c>{undefined, []}</c>, 
	that is, no proxy is configured and 
	<c>https_proxy</c> defaults to the value of <c>proxy</c>.</d>	
	<v>MaxSessions = integer()</v>
        <d>Maximum number of persistent connections to a host.
	Default is <c>2</c>.</d>
	<v>MaxKeepAlive = integer()</v>
	<d>Maximum number of outstanding requests on the same connection to 
	a host. Default is <c>5</c>.</d>
	<v>KeepAliveTimeout = integer()</v>
	<d>If a persistent connection is idle longer than the 
	<c>keep_alive_timeout</c> in milliseconds, 
	the client closes the connection.
	The server can also have such a time-out but do not take that for granted.
	Default is <c>120000</c> (= 2 min).</d>
	<v>MaxPipeline = integer()</v>
	<d>Maximum number of outstanding requests on a pipelined connection 
	to a host. Default is <c>2</c>.</d>
	<v>PipelineTimeout = integer()</v>
	<d>If a persistent connection is idle longer than the 
	<c>pipeline_timeout</c> in milliseconds, 
	the client closes the connection. Default is <c>0</c>,
	which results in pipelining not being used.</d>
        <v>CookieMode = enabled | disabled | verify</v>
        <d>If cookies are enabled, all valid cookies are automatically 
	saved in the cookie database of the client manager.
	If option <c>verify</c> is used, function <c>store_cookies/2</c>
	has to be called for the cookies to be saved. 
	Default is <c>disabled</c>.</d>
	<v>IpFamily = inet | inet6 | local</v>
	<d>Default is <c>inet</c>.</d>
	<v>IpAddress = ip_address()</v>
	<d>If the host has several network interfaces, this option specifies 
	which one to use. 
	See <seealso marker="kernel:gen_tcp#connect">gen_tcp:connect/3,4</seealso> 
	for details.</d>
	<v>Port = integer()</v>
	<d>Local port number to use. 
	See <seealso marker="kernel:gen_tcp#connect">gen_tcp:connect/3,4</seealso> 
	for details.</d>
	<v>socket_opts() = [socket_opt()]</v>
	<d>The options are appended to the socket options used by the 
	client. 
	These are the default values when a new request handler
	is started (for the initial connect). They are passed directly 
        to the underlying transport (<c>gen_tcp</c> or <c>SSL</c>) 
	<em>without</em> verification.</d>
	<v>VerboseMode = false | verbose | debug | trace</v>
	<d>Default is <c>false</c>.
	This option is used to switch on (or off) 
	different levels of Erlang trace on the client. 
	It is a debug feature.</d>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
	<v>UnixSocket = path()</v>
	<d>
	  Experimental option for sending HTTP requests over a unix domain socket. The value
	  of <c>unix_socket</c> shall be the full path to a unix domain socket file with read/write
	  permissions for the erlang process. Default is <c>undefined</c>.
	</d>
      </type>
      <desc>
	<p>Sets options to be used for subsequent requests.</p>
	<note>
	  <p>If possible, the client keeps its connections
	  alive and uses persistent connections
	  with or without pipeline depending on configuration
	  and current circumstances. The HTTP/1.1 specification does not
	  provide a guideline for how many requests that are
	  ideal to be sent on a persistent connection.
	  This depends much on the application.</p>
	  <p>A long queue of requests can cause a
	  user-perceived delay, as earlier requests can take a long time
	  to complete. The HTTP/1.1 specification suggests a
	  limit of two persistent connections per server, which is the
	  default value of option <c>max_sessions</c>.</p>
	</note>

        <marker id="get_options"></marker>
      </desc>
    </func>
     
    <func>
      <name>store_cookies(SetCookieHeaders, Url) -> </name>
      <name>store_cookies(SetCookieHeaders, Url, Profile) -> ok | {error, Reason}</name>
      <fsummary>Saves the cookies defined in <c>SetCookieHeaders</c> in the 
      client profile cookie database.</fsummary>
      <type>
        <v>SetCookieHeaders = headers() - where field = "set-cookie"</v>
        <v>Url = url()</v>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
      </type>
      <desc>
        <p>Saves the cookies defined in <c>SetCookieHeaders</c>
	in the client profile cookie database.
	Call this function if option <c>cookies</c> is set to <c>verify</c>.
	If no profile is specified, the default profile is used.</p>
      </desc>
    </func>

    <func>
      <name>stream_next(Pid) -> ok</name>
      <fsummary>Triggers the next message to be streamed, that is,
	the same behavior as active one for sockets.
      </fsummary>
      <type>
        <v>Pid = pid()</v>
	<d>As received in the <c>stream_start message</c></d>
      </type>
      <desc>
        <p>Triggers the next message to be streamed, that is,
	the same behavior as active ones for sockets.</p>

        <marker id="verify_cookies"></marker>
        <marker id="store_cookies"></marker>
      </desc>
    </func>
    
    <func>
      <name>which_cookies() -> cookies()</name>
      <name>which_cookies(Profile) -> cookies()</name>
      <fsummary>Dumps the entire cookie database.</fsummary>
      <type>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
	<v>cookies() = [cookie_stores()]</v>
	<v>cookie_stores() = {cookies, cookies()} | {session_cookies, cookies()}</v>
	<v>cookies() = [cookie()]</v>
	<v>cookie() = term()</v>
      </type>
      <desc>
        <p>Produces a list of the entire cookie database.
	Intended for debugging/testing purposes. 
	If no profile is specified, the default profile is used.</p>
      </desc>
    </func>

    <func>
      <name>which_sessions() -> session_info()</name>
      <name>which_sessions(Profile) -> session_info()</name>
      <fsummary>Produces a slightly processed dump of the sessions database.</fsummary>
      <type>
	<v>Profile = profile() | pid()</v>
	<d>When started <c>stand_alone</c> only the pid can be used.</d>
	<v>session_info() = {GoodSessions, BadSessions, NonSessions}</v>
	<v>GoodSessions = session()</v>
	<v>BadSessions = tuple()</v>
	<v>NonSessions = term()</v>
      </type>
      <desc>
        <p>Produces a slightly processed dump of the session 
	database. It is intended for debugging. 
	If no profile is specified, the default profile is used.</p>
      </desc>
    </func>

  
  </funcs>

  <section>
    <title>SEE ALSO</title>
    <p><url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>, 
    <seealso marker="inets">inets(3)</seealso>,
    <seealso marker="kernel:gen_tcp">gen_tcp(3)</seealso>, 
    <seealso marker="ssl:ssl">ssl(3)</seealso>
    </p>
  </section>
  
</erlref>