problem understanding code

Questions » problem understanding code

12 years, 7 months ago.

First of all this is the entire example:

#include "mbed.h"
#include "EthernetInterface.h"

int main() {
    EthernetInterface eth;
    eth.init(); //Use DHCP
    eth.connect(75000);
    printf("IP Address is %s\n", eth.getIPAddress());
    
    TCPSocketConnection sock;
    sock.connect("mbed.org", 80);   //connect socket to host
    
    char http_cmd[] = "GET /media/uploads/mbed_official/hello.txt HTTP/1.0\n\n";
    sock.send_all(http_cmd, sizeof(http_cmd)-1);
    
    char buffer[300];
    int ret;
    while (true) {
        ret = sock.receive(buffer, sizeof(buffer)-1);
        if (ret <= 0)
            break;
        buffer[ret] = '\0';
        printf("Received %d chars from server:\n%s\n", ret, buffer);
    }
      
    sock.close();
    
    eth.disconnect();
    
    while(1) {}
}

Im trying to understand the code in this examle:

    TCPSocketConnection sock;
    sock.connect("mbed.org", 80);

this means: the mbed makes a socket connected to his own port nr 80??? and makes a connection to the mbed.org website???

char http_cmd[] = "GET /media/uploads/mbed_official/hello.txt HTTP/1.0\n\n";

this means i put in char http_cmd[] what i get from connecting to the mbed.org/media/.....???

    sock.send_all(http_cmd, sizeof(http_cmd)-1);

this means when someone askes data from the mbed server i send whats in http_cmd???

char buffer[300];
    int ret;
    while (true) {
        ret = sock.receive(buffer, sizeof(buffer)-1);
        if (ret <= 0)
            break;
        buffer[ret] = '\0';
        printf("Received %d chars from server:\n%s\n", ret, buffer);
    }

i dont understand what this does, in hyperterminal i get a lot of information about the server and the connection. but how does sock.receive works???

and most important how do i add event handlers to this program? thnx in advance!

1 Answer

12 years, 7 months ago.

This is what basically happens:

mbed opens a socket to website ''mbed.org". The socket uses port 80, that is the port for http (=browser) traffic. mbed then sends a http "GET" command to that socket to ask for file "/media/uploads/mbed_official/hello.txt". mbed then receives that file from the mbed.org website and prints it in your terminal. You get the text in that file (Hello world!) and some info about the server.

and do you know how to add handlers? is this like with to old library?

posted by Adriaan Van Steendam 05 May 2013

and do you know how to add handlers? is this like with to old library? thnx

posted by Adriaan Van Steendam 05 May 2013

Adriaan Van Steendam

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12 years, 7 months ago.