2017-04-05 03:00:08 +08:00
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.. _http-client-sample:
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2017-01-21 03:03:21 +08:00
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HTTP Client
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###########
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Overview
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********
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This sample application shows how to create HTTP 1.1 requests to
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an HTTP server and how to parse the incoming responses.
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Supported HTTP 1.1 methods are: GET, HEAD, OPTIONS and POST.
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The source code for this sample application can be found at:
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:file:`samples/net/http_client`.
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Requirements
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************
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- Freedom Board (FRDM-K64F)
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- LAN for testing purposes (Ethernet)
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- Terminal emulator software
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- HTTP Server
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Building and Running
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********************
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Open the project configuration file for your platform, for example:
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:file:`prj_frdm_k64f.conf` is the configuration file for the
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:ref:`frdm_k64f` board. For IPv4 networks, set the following variables:
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.. code-block:: console
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CONFIG_NET_IPV4=y
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CONFIG_NET_IPV6=n
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IPv6 is the preferred routing technology for this sample application,
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if CONFIG_NET_IPV6=y is set, the value of CONFIG_NET_IPV4=y is ignored.
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In this sample application, only static IP addresses are supported,
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those addresses are specified in the project configuration file,
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for example:
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.. code-block:: console
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2017-03-15 23:01:47 +08:00
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CONFIG_NET_APP_MY_IPV6_ADDR="2001:db8::1"
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CONFIG_NET_APP_PEER_IPV6_ADDR="2001:db8::2"
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2017-01-21 03:03:21 +08:00
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are the IPv6 addresses for the HTTP client running Zephyr and the
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HTTP server, respectively.
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Alternatively, the IP addresses may be specified in the
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:file:`src/config.h` file.
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Open the :file:`src/config.h` file and set the server port
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to match the HTTP server setup, for example:
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.. code-block:: c
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#define SERVER_PORT 80
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assumes that the HTTP server is listening at the TCP port 80.
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HTTP Server
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===========
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Setting up an HTTP server on your host computer is beyond the scope
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of this document.
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(We used `Apache 2 <http://httpd.apache.org/docs/2.4/getting-started.html>`_
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for testing this sample application.
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However, this application assumes that there is a server's
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resource that can process an HTTP 1.1 POST request.
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For example, assuming that the Apache 2 server with PHP support
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is used, and that the client sends a POST request with
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"Content-Type = application/x-www-form-urlencoded" the following
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PHP script will echo the POST payload back to the client:
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.. code-block:: html
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<html>
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<head>
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<title>HTTP Server POST test</title>
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</head>
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<body>
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<?php
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echo '<p>POST key/values:</p>';
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foreach ($_POST as $key => $value) {
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echo "<p> {$key} : {$value} </p>";
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}
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?>
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</body>
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</html>
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In the machine hosting the HTTP server, this php script is at
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:file:`/var/www/html/post_test.php`. However, for your test machine
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this path can be different, but should be at your server's root folder.
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HTTP Responses
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==============
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Server's responses are processed by the http_receive_cb routine
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defined inside the :file:`src/http_client_rcv.c` file.
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This sample application only prints the HTTP header fields via
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the HTTP Parser Library, see :file:`include/net/http_parser.h`.
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To process the HTTP response's body, use the HTTP Parser's callbacks
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to determine where the body begins. Depending on the payload's size,
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it may be necessary to traverse the network buffer's fragment chain.
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See the :file:`src/http_client_rcv.c` file at line 70 for sample code
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that shows how to walk the fragment chain.
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FRDM K64F
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=========
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Open a terminal window and type:
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.. code-block:: console
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$ make BOARD=frdm_k64f
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The FRDM K64F board is detected as a USB storage device. The board
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must be mounted (i.e. to /mnt) to 'flash' the binary:
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.. code-block:: console
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$ cp outdir/frdm_k64f/zephyr.bin /mnt
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On Linux, use the 'dmesg' program to find the right USB device for the
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FRDM serial console. Assuming that this device is ttyACM0, open a
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terminal window and type:
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.. code-block:: console
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$ screen /dev/ttyACM0 115200
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Once the binary is loaded into the FRDM board, press the RESET button.
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Refer to the board documentation in Zephyr, :ref:`frdm_k64f`,
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for more information about this board and how to access the FRDM
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serial console under other operating systems.
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Sample Output
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=============
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This sample application loops a specified number of times doing four
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HTTP 1.1 requests and displays the header fields that were extracted
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from the server's response. The four requests are:
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- GET "/index.html"
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- HEAD "/"
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- OPTIONS "/"
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- POST "/post_test.php"
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The terminal window where screen is running will show something similar
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to the following:
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.. code-block:: console
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*******************************************
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HTTP Client: 2001:db8::1
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Connecting to: 2001:db8::2 port 80
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Hostname: 2001:db8::2
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HTTP Request: GET
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--------- HTTP response (headers) ---------
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Date: Thu, 02 Feb 2017 00:51:31 GMT
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Server: Apache/2.4.10 (Debian)
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Last-Modified: Sat, 28 Jan 2017 02:55:09 GMT
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ETag: "3c-5471eb5db3c73"
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Accept-Ranges: bytes
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Content-Length: 60
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Connection: close
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Content-Type: text/html
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HTTP server response status: OK
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HTTP parser status: success
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HTTP body: 60 bytes, expected: 60 bytes
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*******************************************
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HTTP Client: 2001:db8::1
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Connecting to: 2001:db8::2 port 80
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Hostname: 2001:db8::2
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HTTP Request: HEAD
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--------- HTTP response (headers) ---------
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Date: Thu, 02 Feb 2017 00:51:37 GMT
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Server: Apache/2.4.10 (Debian)
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Last-Modified: Sat, 28 Jan 2017 02:55:09 GMT
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ETag: "3c-5471eb5db3c73"
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Accept-Ranges: bytes
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Content-Length: 60
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Connection: close
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Content-Type: text/html
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HTTP server response status: OK
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HTTP parser status: success
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*******************************************
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HTTP Client: 2001:db8::1
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Connecting to: 2001:db8::2 port 80
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Hostname: 2001:db8::2
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HTTP Request: OPTIONS
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--------- HTTP response (headers) ---------
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Date: Thu, 02 Feb 2017 00:51:43 GMT
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Server: Apache/2.4.10 (Debian)
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Allow: GET,HEAD,POST,OPTIONS
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Content-Length: 0
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Connection: close
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Content-Type: text/html
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HTTP server response status: OK
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HTTP parser status: success
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*******************************************
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HTTP Client: 2001:db8::1
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Connecting to: 2001:db8::2 port 80
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Hostname: 2001:db8::2
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HTTP Request: POST
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--------- HTTP response (headers) ---------
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Date: Thu, 02 Feb 2017 00:51:49 GMT
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Server: Apache/2.4.10 (Debian)
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Vary: Accept-Encoding
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Content-Length: 231
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Connection: close
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Content-Type: text/html; charset=UTF-8
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HTTP server response status: OK
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HTTP parser status: success
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