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<chapter>
  <header>
    <copyright>
      <year>2004</year><year>2021</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
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    </legalnotice>

    <title>HTTP Client</title>
    <prepared>Ingela Anderton Andin</prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date></date>
    <rev></rev>
    <file>http_client.xml</file>
  </header>

  <section>
    <title>Configuration</title>

      <p>The HTTP client default profile is started when the <c>Inets</c>
    application is started and is then available to all processes on
    that Erlang node. Other profiles can also be started at
    application startup, or profiles can be started and stopped
    dynamically in runtime. Each client profile spawns a new
    process to handle each request, unless a persistent connection 
    can be used with or without pipelining.
    The client adds a <c>host</c> header and an empty
    <c>te</c> header if there are no such headers present in the request.</p>

    <p>The client supports IPv6 as long as the underlying mechanisms also do
      so.</p>

    <p>The following is to be put in the Erlang node application configuration file
      to start a profile at application startup:</p>
    <pre>
      [{inets, [{services, [{httpc, PropertyList}]}]}]</pre>
    <p>For valid properties, see 
    <seeerl marker="httpc">httpc(3)</seeerl>. </p>
  </section>

  <section>
    <title>Getting Started</title>
    <p>Start <c>Inets</c>:</p>
    <code type="erl">
 1 > inets:start().
      ok</code>
    <p>The following calls use the default client profile.
      Use the proxy <c>"www-proxy.mycompany.com:8000"</c>,
      except from requests to localhost. This applies to all the
      following requests.</p>
      <p>Example:</p>
    <code type="erl">
      2 > httpc:set_options([{proxy, {{"www-proxy.mycompany.com", 8000},
      ["localhost"]}}]).
      ok</code>
    <p>The following is an ordinary synchronous request:</p>
    <code type="erl">
      3 > {ok, {{Version, 200, ReasonPhrase}, Headers, Body}} =
      httpc:request(get, {"http://www.erlang.org", []}, [], []).</code>
    <p>With all the default values presented, a get request can also be written
      as follows:</p>
    <code type="erl">
      4 > {ok, {{Version, 200, ReasonPhrase}, Headers, Body}} =
      httpc:request("http://www.erlang.org").</code>
    <p>The following is an ordinary asynchronous request:</p>
    <code type="erl">
      5 > {ok, RequestId} =
      httpc:request(get, {"http://www.erlang.org", []}, [], [{sync, false}]).</code>
      <p>The result is sent to the calling process as
      <c>{http, {ReqestId, Result}}</c>.</p>
    <p>In this case, the calling process is the shell, so the following
      result is received:</p>
    <code type="erl">
      6 > receive {http, {RequestId, Result}} -> ok after 500 -> error end.
      ok</code>
    <p>This sends a request with a specified connection header:</p>
    <code type="erl">
      7 > {ok, {{NewVersion, 200, NewReasonPhrase}, NewHeaders, NewBody}} =
      httpc:request(get, {"http://www.erlang.org", [{"connection", "close"}]},
      [], []).</code>
    <p>This sends an HTTP request over a unix domain socket (experimental):</p>
    <code type="erl">
      8 > httpc:set_options([{ipfamily, local},
      {unix_socket,"/tmp/unix_socket/consul_http.sock"}]).
      9 > {ok, {{NewVersion, 200, NewReasonPhrase}, NewHeaders, NewBody}} =
      httpc:request(put, {"http:///v1/kv/foo", [], [], "hello"}, [], []).</code>
    <p>Start an HTTP client profile:</p>
   
    <code><![CDATA[
      10 > {ok, Pid} = inets:start(httpc, [{profile, foo}]).
      {ok, <0.45.0>}       
      ]]></code>
    
    <p>The new profile has no proxy settings, so the connection is refused:</p>
      <code type="erl">
      11 > httpc:request("http://www.erlang.org", foo).
      {error, econnrefused}</code>

    <p>Stop the HTTP client profile:</p>
    <code type="erl">
      12 > inets:stop(httpc, foo).
      ok</code>
    
    <p>Alternative way to stop the HTTP client profile:</p>
    <code type="erl">
      13 > inets:stop(httpc, Pid).
      ok</code>
    
  </section>
</chapter>




