HTTP and HTTPS example application for Mbed OS 5

Dependencies:   mbed-http

This application demonstrates how to make HTTP and HTTPS requests and parse the response from Mbed OS 5.

It consists of six example applications, which you can select in source/select-demo.h:

Response parsing is done through nodejs/http-parser.

Note: HTTPS requests do not work on targets with less than 128K of RAM due to the size of the TLS handshake. For more background see mbed-http.

To build

  1. If you're using WiFi, specify the credentials in mbed_app.json.
  2. Build the project in the online compiler or using Mbed CLI.
  3. Flash the project to your development board.
  4. Attach a serial monitor to your board to see the debug messages.

Defining the network interface

This application uses the on-board network interface for your board. If you use an external network interface (f.e. a WiFi module) you need to add the driver to this project. Then, open network-helper.h and specify which network driver to use.

More information is in the Mbed OS documentation under IP Networking.

Entropy (or lack thereof)

On all platforms that do not have the TRNG feature, the application is compiled without TLS entropy sources. This means that your code is inherently unsafe and should not be deployed to any production systems. To enable entropy, remove the MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES and MBEDTLS_TEST_NULL_ENTROPY macros from mbed_app.json.

Flash size

Default flash size for HTTPS is very large, as the application is loading the default Mbed TLS configuration. To use a more optimized version, you can disable unused cypher suites and other Mbed TLS features with a custom configuration file. Create a new configuration file, then add in mbed_app.json:

"MBEDTLS_CONFIG_FILE=\"mbedtls_config.h\""

to the macros array.

Running tests

You can run the integration tests from this project via Mbed CLI.

  1. In select-demo.h set the DEMO macro to DEMO_TESTS.
  2. Set your WiFi credentials in mbed_app.json.
  3. Then run the tests via:

$ mbed test -v -n mbed-http-tests-tests-*

Tested on

  • K64F with Ethernet.
  • NUCLEO_F411RE with ESP8266 (not working on Mbed OS 5.12+)
  • ODIN-W2 with WiFi.
  • K64F with Atmel 6LoWPAN shield.
  • DISCO-L475VG-IOT01A with WiFi (requires the wifi-ism43362 driver).
Revision:
1:3bff14db67c7
diff -r 85fdc69bc10c -r 3bff14db67c7 source/mbed-http/http_request.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/mbed-http/http_request.h	Thu Feb 16 11:13:40 2017 +0100
@@ -0,0 +1,180 @@
+#ifndef _HTTP_REQUEST_
+#define _HTTP_REQUEST_
+
+#include <string>
+#include <vector>
+#include <map>
+#include "http_parser.h"
+#include "http_response.h"
+#include "http_request_builder.h"
+#include "http_response_parser.h"
+#include "http_parsed_url.h"
+
+/**
+ * @todo:
+ *      - Userinfo parameter is not handled
+ *      - Allow socket re-use
+ */
+
+
+/**
+ * \brief HttpRequest implements the logic for interacting with HTTPS servers.
+ */
+class HttpRequest {
+public:
+    /**
+     * HttpRequest Constructor
+     *
+     * @param[in] aNetwork The network interface
+     * @param[in] aMethod HTTP method to use
+     * @param[in] url URL to the resource
+     * @param[in] aBodyCallback Callback on which to retrieve chunks of the response body.
+                                If not set, the complete body will be allocated on the HttpResponse object,
+                                which might use lots of memory.
+    */
+    HttpRequest(NetworkInterface* aNetwork, http_method aMethod, const char* url, Callback<void(const char *at, size_t length)> aBodyCallback = 0)
+        : network(aNetwork), method(aMethod), body_callback(aBodyCallback)
+    {
+        error = 0;
+        response = NULL;
+
+        parsed_url = new ParsedUrl(url);
+        request_builder = new HttpRequestBuilder(method, parsed_url);
+    }
+
+    /**
+     * HttpRequest Constructor
+     */
+    ~HttpRequest() {
+        // should response be owned by us? Or should user free it?
+        // maybe implement copy constructor on response...
+        if (response) {
+            delete response;
+        }
+
+        if (parsed_url) {
+            delete parsed_url;
+        }
+
+        if (request_builder) {
+            delete request_builder;
+        }
+    }
+
+    /**
+     * Execute the request and receive the response.
+     */
+    HttpResponse* send(const void* body = NULL, nsapi_size_t body_size = 0) {
+        if (response != NULL) {
+            // already executed this response
+            error = -2100; // @todo, make a lookup table with errors
+            return NULL;
+        }
+
+        error = 0;
+
+        TCPSocket socket;
+
+        nsapi_error_t open_result = socket.open(network);
+        if (open_result != 0) {
+            error = open_result;
+            return NULL;
+        }
+
+        nsapi_error_t connection_result = socket.connect(parsed_url->host(), parsed_url->port());
+        if (connection_result != 0) {
+            error = connection_result;
+            return NULL;
+        }
+
+        char* request = request_builder->build(body, body_size);
+        size_t request_size = strlen(request);
+
+        nsapi_size_or_error_t send_result = socket.send(request, request_size);
+
+        free(request);
+
+        if (send_result != request_size) {
+            error = send_result;
+            return NULL;
+        }
+
+        // Create a response object
+        response = new HttpResponse();
+        // And a response parser
+        HttpResponseParser parser(response, body_callback);
+
+        // Set up a receive buffer (on the heap)
+        uint8_t* recv_buffer = (uint8_t*)malloc(HTTP_RECEIVE_BUFFER_SIZE);
+
+        // TCPSocket::recv is called until we don't have any data anymore
+        nsapi_size_or_error_t recv_ret;
+        while ((recv_ret = socket.recv(recv_buffer, HTTP_RECEIVE_BUFFER_SIZE)) > 0) {
+            // Pass the chunk into the http_parser
+            size_t nparsed = parser.execute((const char*)recv_buffer, recv_ret);
+            if (nparsed != recv_ret) {
+                // printf("Parsing failed... parsed %d bytes, received %d bytes\n", nparsed, recv_ret);
+                error = -2101;
+                free(recv_buffer);
+                return NULL;
+            }
+            // No more chunks? break out of this loop
+            if (recv_ret < HTTP_RECEIVE_BUFFER_SIZE) {
+                break;
+            }
+        }
+        // error?
+        if (recv_ret < 0) {
+            error = recv_ret;
+            free(recv_buffer);
+            return NULL;
+        }
+
+        // When done, call parser.finish()
+        parser.finish();
+
+        // Free the receive buffer
+        free(recv_buffer);
+
+        // Close the socket
+        socket.close();
+
+        return response;
+    }
+
+    /**
+     * Set a header for the request.
+     *
+     * The 'Host' and 'Content-Length' headers are set automatically.
+     * Setting the same header twice will overwrite the previous entry.
+     *
+     * @param[in] key Header key
+     * @param[in] value Header value
+     */
+    void set_header(string key, string value) {
+        request_builder->set_header(key, value);
+    }
+
+    /**
+     * Get the error code.
+     *
+     * When send() fails, this error is set.
+     */
+    nsapi_error_t get_error() {
+        return error;
+    }
+
+private:
+    NetworkInterface* network;
+    http_method method;
+    Callback<void(const char *at, size_t length)> body_callback;
+
+    ParsedUrl* parsed_url;
+
+    HttpRequestBuilder* request_builder;
+    HttpResponse* response;
+
+    nsapi_error_t error;
+};
+
+#endif // _HTTP_REQUEST_