File content as of revision 4:31010e482971:

/* 
 * In this example LED1 on the mbed board is turned on/off using a web browser.
 * However, you can easily modify the project to remotely switch on/off any external device.
 * The HTTP server is built from an mbed board and a WIZ550io board.
 * The example is based on the Tuxgraphics Web Switch <http://www.tuxgraphics.org/>.
 * Thanks to Jozsef Voros it works now also with the W5500 modules without a built-in MAC
 * See below how to enable that.
 */
#include "mbed.h"
#include "EthernetInterface.h"
#include <string>

using namespace     std;

Serial              serial(USBTX, USBRX);

#if defined(TARGET_LPC1768)
EthernetInterface   eth(p11, p12, p13, p8, p14);        // MOSI, MISO, SCK, CS, RESET
#elif defined(TARGET_LPC11U24)
EthernetInterface   eth(P16, P15, P13, P17, P18);       // MOSI, MISO, SCK, CS, RESET
#elif defined(TARGET_NUCLEO_F103RB) || defined(TARGET_NUCLEO_L152RE) || defined(TARGET_NUCLEO_F030R8)  \
   || defined(TARGET_NUCLEO_F401RE) || defined(TARGET_NUCLEO_F302R8) || defined(TARGET_NUCLEO_L053R8)  \
   || defined(TARGET_NUCLEO_F411RE) || defined(TARGET_NUCLEO_F334R8) || defined(TARGET_NUCLEO_F072RB)  \
   || defined(TARGET_NUCLEO_F091RC) || defined(TARGET_NUCLEO_F303RE) || defined(TARGET_NUCLEO_F070RB)  \
   || defined(TARGET_KL25Z ) || defined(TARGET_KL46Z) || defined(TARGET_K64F) || defined(TARGET_KL05Z) \
   || defined(TARGET_K20D50M) || defined(TARGET_K22F) \
   || defined(TARGET_NRF51822) \
   || defined(TARGET_RZ_A1H)
EthernetInterface   eth(D4, D5, D3, D6, D7); // MOSI, MISO, SCK, CS, RESET

// If your board/plaform is not present yet then uncomment
// the following two lines and replace modify as appropriate.

//#elif defined(TARGET_YOUR_BOARD)
//EthernetInterface   eth(SPI_MOSI, SPI_MISO, SPI_SCK, SPI_CS, RESET); // MOSI, MISO, SCK, CS, RESET
#endif

// Note:
// If it happends that any of the SPI_MOSI, SPI_MISO, SPI_SCK, SPI_CS or RESET pins collide with LED1 pin
// then either use different SPI port (if available on the board) and change the pin names
// in the constructor spi(...) accordingly or instead of using LED1 pin, select
// a free pin (not used by SPI port) and connect to it an external LED which is connected
// to a 220 Ohm resitor that is connected to the groud.
// In the second case remember to replace LED1 in sw(LED1) constructor (see below).
// IP address must be also unique and compatible with your network. Change as appropriate.

// If intead of WIZ550io you'd like to use a W5500 module without a built-in MAC please uncommend the following line
#define W5500   1

#if defined(W5500)
// The MAC number must be unique within the connected network. Modify as appropriate.
uint8_t       MY_MAC[6] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05 };
#endif

const char          MY_IP[] = "192.168.1.181";
const char          MY_NETMASK[] = "255.255.255.0";
const char          MY_GATEWAY[] = "192.168.1.1";
int                 MY_PORT = 80;

TCPSocketServer     server;
TCPSocketConnection client;
bool                serverIsListening = false;

DigitalOut          sw(LED1);   // Change LED1 to a pin of your choice.
                                // However, make sure that it does not collide with any of the SPI pins

const string        PASSWORD = "secret";    // change as you like
const string        HTTP_OK = "HTTP/1.0 200 OK";
const string        permanentlyMoved = "HTTP/1.0 301 Moved Permanently\r\nLocation: ";
const string        UNAUTHORIZED = "HTTP/1.0 401 Unauthorized";

string              httpHeader;     // HTTP header
string              httpContent;    // HTTP content

// analyse the url given
// return values: -1 invalid password
//                -2 no command given but password valid
//                -3 just refresh page
//                 0 switch off
//                 1 switch on
//
//                The string passed to this function will look like this:
//                GET /password HTTP/1.....
//                GET /password/ HTTP/1.....
//                GET /password/?sw=1 HTTP/1.....

//                GET /password/?sw=0 HTTP/1.....
int8_t analyseGetURL(string& str) {
    if(str.substr(5, PASSWORD.size()) != PASSWORD)
        return(-1);

    uint8_t pos = 5 + PASSWORD.size();

    if(str.substr(pos, 1) == " ")
        return(-2);

    if(str.substr(pos, 1) != "/")
        return(-1);

    pos++;

    string  cmd(str.substr(pos, 5));

    if(cmd == "?sw=0")
        return(0);

    if(cmd == "?sw=1")
        return(1);

    return(-3);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
string& movedPermanently(uint8_t flag) {
    if(flag == 1)
        httpContent = "/" + PASSWORD + "/";
    else
        httpContent = "";

    httpContent += "<h1>301 Moved Permanently</h1>\r\n";

    return(httpContent);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
string& view(uint8_t status) {
    httpContent = "<h2>Web Switch</h2>\r\n";

    if(status == 1) {
        httpContent += "<pre>\r\n  <font color=#FF0000>ON</font>";
        httpContent += " <a href=\"./?sw=0\">[switch off]</a>\r\n";
    }
    else {
        httpContent += "<pre>\r\n  <font color=#00FF00>OFF</font>";
        httpContent += " <a href=\"./?sw=1\">[switch on]</a>\r\n";
    }

    httpContent += "  <a href=\".\">[refresh status]</a>\r\n";
    httpContent += "</pre>\r\n";
    httpContent += "<hr>\r\n";
    return httpContent;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void sendHTTP(TCPSocketConnection& client, string& header, string& content) {
    char    contentLeght[5] = { };

    header += "\r\nContent-Type: text/html\r\n";
    header += "Content-Length: ";
    sprintf(contentLeght, "%d", content.length());
    header += string(contentLeght) + "\r\n";
    header += "Pragma: no-cache\r\n";
    header += "Connection: About to close\r\n";
    header += "\r\n";

    string  webpage = header + content;
    client.send (const_cast<char*>(webpage.c_str ()), webpage.length ());
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void closeClient(void) {
    client.close();
    serial.printf("Connection closed.\n\rTCP server is listening...\n\r");
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
int main(void) {
#if defined(W5500)
    int     ret = eth.init(MY_MAC, MY_IP, MY_NETMASK, MY_GATEWAY);
#else
    int     ret = eth.init(MY_IP, MY_NETMASK, MY_GATEWAY);
#endif
    if(!ret) {
        serial.printf("Initialized, MY_MAC: %s\n", eth.getMACAddress());
        serial.printf
            (
                "Connected, MY_IP: %s, MY_NETMASK: %s, MY_GATEWAY: %s\n",
                eth.getIPAddress(),
                eth.getNetworkMask(),
                eth.getGateway()
            );
    }
    else {
        serial.printf("Error eth.init() - ret = %d\n", ret);
        return -1;
    }

    //setup tcp socket
    if(server.bind(MY_PORT) < 0) {
        serial.printf("TCP server bind failed.\n\r");
        return -1;
    }
    else {
        serial.printf("TCP server bind succeeded.\n\r");
        serverIsListening = true;
    }

    if(server.listen(1) < 0) {
        serial.printf("TCP server listen failed.\n\r");
        return -1;
    }
    else {
        serial.printf("TCP server is listening...\n\r");
    }

    while(serverIsListening) {
        if(server.accept(client) >= 0) {
            char    buf[1024] = { };
            size_t  size = 0;
            
            serial.printf("Client connected!\n\rIP: %s\n\r", client.get_address());
            
            switch(client.receive(buf, 1023)) {
            case 0:
                serial.printf("Recieved buffer is empty.\n\r");
                break;

            case -1:
                serial.printf("Failed to read data from client.\n\r");
                break;

            default:
                size = strlen(buf);

                string  received((char*)buf);

                if(received.substr(0, 3) != "GET") {
                    httpHeader = HTTP_OK;
                    httpContent = "<h1>200 OK</h1>";
                    sendHTTP(client, httpHeader, httpContent);
                    closeClient();
                    continue;
                }

                if(received.substr(0, 6) == "GET / ") {
                    httpHeader = HTTP_OK;
                    httpContent = "<p>Usage: http://host_or_ip/password</p>\r\n";
                    sendHTTP(client, httpHeader, httpContent);
                    closeClient();
                    continue;
                }

                int cmd = analyseGetURL(received);

                if(cmd == -2) {

                    // redirect to the right base url
                    httpHeader = permanentlyMoved;
                    sendHTTP(client, httpHeader, movedPermanently(1));
                    closeClient();
                    continue;
                }

                if(cmd == -1) {
                    httpHeader = UNAUTHORIZED;
                    httpContent = "<h1>401 Unauthorized</h1>";
                    sendHTTP(client, httpHeader, httpContent);
                    closeClient();
                    continue;
                }

                if(cmd == 1) {
                    sw = 1; // switch on
                }

                if(cmd == 0) {
                    sw = 0; // switch off
                }

                httpHeader = HTTP_OK;
                sendHTTP(client, httpHeader, view(sw));
            }
            closeClient();
        }
    }
}