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Wi-Fi

The WifiInterface provides a simple C++ API for connecting to the internet over a Wi-Fi device.

There are multiple Wi-Fi components that implement the WiFiInterface class. The example below uses the ESP8266Interface.

Wi-Fi class reference

Public Member Functions
virtual ~WiFiInterface ()
virtual nsapi_error_t set_credentials (const char *ssid, const char *pass, nsapi_security_t security=NSAPI_SECURITY_NONE)=0
virtual nsapi_error_t set_channel (uint8_t channel)=0
virtual int8_t get_rssi ()=0
virtual nsapi_error_t connect (const char *ssid, const char *pass, nsapi_security_t security=NSAPI_SECURITY_NONE, uint8_t channel=0)=0
virtual nsapi_error_t connect ()=0
virtual nsapi_error_t disconnect ()=0
virtual nsapi_size_or_error_t scan (WiFiAccessPoint *res, nsapi_size_t count)=0
 Public Member Functions inherited from NetworkInterface
virtual const char * get_mac_address ()
virtual const char * get_ip_address ()
virtual const char * get_netmask ()
virtual const char * get_gateway ()
virtual nsapi_error_t set_network (const char *ip_address, const char *netmask, const char *gateway)
virtual nsapi_error_t set_dhcp (bool dhcp)
virtual nsapi_error_t gethostbyname (const char *host, SocketAddress *address, nsapi_version_t version=NSAPI_UNSPEC)
virtual nsapi_error_t add_dns_server (const SocketAddress &address)
Additional Inherited Members
 Protected Member Functions inherited from NetworkInterface
virtual NetworkStackget_stack ()=0

Usage

To bring up the network interface:

  1. Instantiate an implementation of the WiFiInterface class (for example, the ESP8266Interface).
  2. Call the connect function with an SSID and password for the Wi-Fi network.
  3. Once connected, the WiFiInterface can be used as a target for opening network sockets.

Wi-Fi example

Here is an example of an HTTP client program. The program brings up an ESP8266 as the underlying network interface, and uses it to perform an HTTP transaction over a TCPSocket:

/* WiFi Example
 * Copyright (c) 2016 ARM Limited
 *
 * 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.
 */

#include "mbed.h"
#include "TCPSocket.h"

#if TARGET_UBLOX_EVK_ODIN_W2
#include "OdinWiFiInterface.h"
OdinWiFiInterface wifi;
#else
#if !TARGET_FF_ARDUINO
#error [NOT_SUPPORTED] Only Arduino form factor devices are supported at this time
#endif
#include "ESP8266Interface.h"
ESP8266Interface wifi(D1, D0);
#endif

const char *sec2str(nsapi_security_t sec)
{
    switch (sec) {
        case NSAPI_SECURITY_NONE:
            return "None";
        case NSAPI_SECURITY_WEP:
            return "WEP";
        case NSAPI_SECURITY_WPA:
            return "WPA";
        case NSAPI_SECURITY_WPA2:
            return "WPA2";
        case NSAPI_SECURITY_WPA_WPA2:
            return "WPA/WPA2";
        case NSAPI_SECURITY_UNKNOWN:
        default:
            return "Unknown";
    }
}

void scan_demo(WiFiInterface *wifi)
{
    WiFiAccessPoint *ap;

    printf("Scan:\r\n");

    int count = wifi->scan(NULL,0);

    /* Limit number of network arbitrary to 15 */
    count = count < 15 ? count : 15;

    ap = new WiFiAccessPoint[count];
    count = wifi->scan(ap, count);
    for (int i = 0; i < count; i++)
    {
        printf("Network: %s secured: %s BSSID: %hhX:%hhX:%hhX:%hhx:%hhx:%hhx RSSI: %hhd Ch: %hhd\r\n", ap[i].get_ssid(),
               sec2str(ap[i].get_security()), ap[i].get_bssid()[0], ap[i].get_bssid()[1], ap[i].get_bssid()[2],
               ap[i].get_bssid()[3], ap[i].get_bssid()[4], ap[i].get_bssid()[5], ap[i].get_rssi(), ap[i].get_channel());
    }
    printf("%d networks available.\r\n", count);

    delete[] ap;
}

void http_demo(NetworkInterface *net)
{
    TCPSocket socket;

    printf("Sending HTTP request to www.arm.com...\r\n");

    // Open a socket on the network interface, and create a TCP connection to www.arm.com
    socket.open(net);
    socket.connect("www.arm.com", 80);

    // Send a simple http request
    char sbuffer[] = "GET / HTTP/1.1\r\nHost: www.arm.com\r\n\r\n";
    int scount = socket.send(sbuffer, sizeof sbuffer);
    printf("sent %d [%.*s]\r\n", scount, strstr(sbuffer, "\r\n")-sbuffer, sbuffer);

    // Recieve a simple http response and print out the response line
    char rbuffer[64];
    int rcount = socket.recv(rbuffer, sizeof rbuffer);
    printf("recv %d [%.*s]\r\n", rcount, strstr(rbuffer, "\r\n")-rbuffer, rbuffer);

    // Close the socket to return its memory and bring down the network interface
    socket.close();
}

int main()
{
    printf("WiFi example\r\n\r\n");

    scan_demo(&wifi);

    printf("\r\nConnecting...\r\n");
    int ret = wifi.connect(MBED_CONF_APP_WIFI_SSID, MBED_CONF_APP_WIFI_PASSWORD, NSAPI_SECURITY_WPA_WPA2);
    if (ret != 0) {
        printf("\r\nConnection error\r\n");
        return -1;
    }

    printf("Success\r\n\r\n");
    printf("MAC: %s\r\n", wifi.get_mac_address());
    printf("IP: %s\r\n", wifi.get_ip_address());
    printf("Netmask: %s\r\n", wifi.get_netmask());
    printf("Gateway: %s\r\n", wifi.get_gateway());
    printf("RSSI: %d\r\n\r\n", wifi.get_rssi());

    http_demo(&wifi);

    wifi.disconnect();

    printf("\r\nDone\r\n");
}

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