Thread: Web-Client program using TCP/IP streaming sockets ( winsock )

Hello, I finally got around to trying to complete my objective in networking I mentioned so long ago. I'm having a spot of trouble connecting to the web-server right now though.

The error message I'm getting is from the connect() function :

Code:

connect failed with : 10047,
System Remark : An address incompatible with the requested protocol was used.

I looked it up, and I found that it had to do with not choosing the correct protocol format. I looked over my code a lot, and I didn't see how I wasn't using the correct protocol. I formatted it for IPv4 and IPv6 correctly didn't I? I'm not sure what I need to change to get it to work.

Code:

#include <stdio.h>
#include <stdlib.h>


/* Define the Windows version, so microsoft won't have a heart attack */
#define _WIN32_WINNT 0x0501


#include <winsock2.h>
#include <Ws2tcpip.h>


/* Silence those pesky compiler warnings about unused variables */
#define UNUSED_DATA( data ) ( ( void )data )


typedef union internet_protocol_version
{
    struct sockaddr_in6 v6; /* IPv6 */
    struct sockaddr_in v4; /* IPv4 */
} internet_protocol_version;


typedef struct internet_data
{
    internet_protocol_version protcol_version;


    unsigned short family;
    int socket;


    struct addrinfo hints;
    struct addrinfo * server_info;


} internet_data;


WSADATA setup_winsock( );


void init_hints( internet_data * data );
void get_host_info( const char * domain, const char * service, internet_data * data );
int try_connect( internet_data * data );
void connect_to_host( internet_data * data );


void free_winsock( );


WSADATA setup_winsock( )
{
    int status = 0;
    /*
          WSADATA is a structure that contains information about the current
    system's networking capabilities. It's uneeded in my case.
    */
    WSADATA wsa_data;


    /* Let's be futuristic and use version 2.2 of Winsock */
    if ( ( status = WSAStartup( MAKEWORD( 2, 2 ), &wsa_data ) ) )
    {
        fprintf( stderr, "WSAStartup failed, System remark : %s\n", gai_strerror( status ) );
        exit( 1 );
    }


    return wsa_data;
}


void init_hints( internet_data * data )
{
    memset( &data->hints, 0, sizeof( struct addrinfo ) ); /* Zero out the hints structure */
    data->hints.ai_family = AF_UNSPEC; /* We don't care about IPv4 or IPv6 */
    data->hints.ai_socktype = SOCK_STREAM; /* We want TCP stream sockets */
    data->hints.ai_flags = AI_PASSIVE; /* Fill in our local IP address */


    return;
}


void get_host_info( const char * domain, const char * service, internet_data * data )
{
    int status = 0;


    if ( ( status = getaddrinfo( domain, service, &data->hints, &data->server_info ) ) )
    {
        fprintf( stderr, "getaddrinfo failed, System remark : %s\n", gai_strerror( status ) );
        free_winsock( );
        exit( 2 );
    }


    return;
}


int try_connect( internet_data * data )
{
    if ( data->family == AF_INET ) /* If IPv4... */
    {
        if ( connect( data->socket, ( struct sockaddr * )&data->protcol_version.v4, sizeof( struct sockaddr ) ) == SOCKET_ERROR )
        {
            fprintf( stderr, "connect failed with : %d,\nSystem Remark : %s\n", WSAGetLastError( ), gai_strerror( WSAGetLastError( ) ) );
            return 0;
        }


        return 1;
    }
    else /* If IPv6... */
    {
        if ( connect( data->socket, ( struct sockaddr * )&data->protcol_version.v6, sizeof( struct sockaddr ) ) == SOCKET_ERROR )
        {
            fprintf( stderr, "connect failed with : %d,\nSystem Remark : %s\n", WSAGetLastError( ), gai_strerror( WSAGetLastError( ) ) );
            return 0;
        }


        return 1;
    }


    return 0;
}


void connect_to_host( internet_data * data )
{
    struct addrinfo * temp = NULL;


    for ( temp = data->server_info; temp; temp = temp->ai_next )
    {
        if ( temp->ai_family == AF_INET ) /* If IPv4... */
        {
            data->protcol_version.v4 = *( struct sockaddr_in * )temp;
            data->family = AF_INET;


            /* Use TCP/IP with streaming sockets and IPV4 */
            data->socket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );


            if ( data->socket == INVALID_SOCKET )
            {
                fprintf( stderr, "socket failed with : %d,\nSystem Remark : %s\n", WSAGetLastError( ), gai_strerror( WSAGetLastError( ) ) );
                continue;
            }
            else
            {
                if ( try_connect( data ) ) /* If connected... */
                    return; /* Return to main. */
                else /* else, close the socket and continue the loop. */
                {
                    closesocket( data->socket );
                    continue;
                }
            }
        }
        else if ( temp->ai_family == AF_INET6 ) /* If IPv6... */
        {
            data->protcol_version.v6 = *( struct sockaddr_in6 * )temp;
            data->family = AF_INET6;


            /* Use TCP/IP with streaming sockets and IPV6 */
            data->socket = socket( AF_INET6, SOCK_STREAM, IPPROTO_TCP );


            if ( data->socket == INVALID_SOCKET )
            {
                fprintf( stderr, "socket failed with : %d,\nSystem Remark : %s\n", WSAGetLastError( ), gai_strerror( WSAGetLastError( ) ) );
                continue;
            }
            else
            {
                if ( try_connect( data ) ) /* If connected... */
                    return; /* Return to main. */
                else /* else, close the socket and continue the loop. */
                {
                    closesocket( data->socket );
                    continue;
                }
            }
        }


        break;
    }


    fprintf( stderr, "\nCouldn't connect to server!\n" );
    freeaddrinfo( data->server_info );
    free_winsock( );
    exit( 2 );
}


void free_winsock( )
{
    /* Let's free whatever resources our Windows OS wanted to use... */


    if ( WSACleanup() )
    {
        fprintf( stderr, "WSACleanup failed with : %d,\nSystem Remark : %s\n", WSAGetLastError( ), gai_strerror( WSAGetLastError( ) ) );
        exit( 3 );
    }


    return;
}


int main( )
{
    WSADATA wsa_data = { 0 };


    internet_data my_data;


    /* Set up */
    wsa_data = setup_winsock( );
    UNUSED_DATA( wsa_data ); /* Inhibit compiler warnings */


    init_hints( &my_data ); /* Setup our preferences */
    get_host_info( "www.yahoo.com", "smtp", &my_data ); /* Get information about the host */
    connect_to_host( &my_data ); /* Connect to the host with the information we got earlier */


    /* Clean up */
    closesocket( my_data.socket );
    freeaddrinfo( my_data.server_info );


    free_winsock( );


    return 0;
}

I'm linking with w2_32.dll.

Originally Posted by tabstop

MSDN says this about AI_PASSIVE.

Huh, I didn't know that it meant I had to bind. I was using Beej's tutorial, I guess that's an area where Unix and Windows aren't the same. Anyways, there were some new problems that have arisen after fixing the AI_PASSIVE problem. I did more research( namely, Complete Winsock Client Code (Windows) ), and used microsoft's sample code to fix some of my function calls.

Here are the changes I made in the above code I posted :

I changed my data structure to this :

Code:

typedef struct internet_data
{
    unsigned short family;
    int socket;


    struct addrinfo hints;
    struct addrinfo * server_info;


} internet_data;

I changed my socket call to this :

Code:

data->socket = socket( temp->ai_family, temp->ai_socktype, temp->ai_protocol );

I changed my try_connect function call to this :

Code:

int try_connect( internet_data * data, struct addrinfo * node )
{
    if ( connect( data->socket, ( struct sockaddr * )node->ai_addr, ( int )node->ai_addrlen ) == SOCKET_ERROR )
    {
        fprintf( stderr, "connect failed with : %d,\nSystem Remark : %s\n", WSAGetLastError( ), gai_strerror( WSAGetLastError( ) ) );
        return 0;
    }


    printf( "Connected to host!\n" );
    return 1;
}

I changed my get_host_info call to this( using http as a control test ) :

Code:

get_host_info( "www.yahoo.com", "http", &my_data ); /* Get information about the host */

Finally, I changed my main call to this :

Code:

int main( )
{
    WSADATA wsa_data = { 0 };


    internet_data my_data;


    /* Set up */
    wsa_data = setup_winsock( );
    UNUSED_DATA( wsa_data ); /* Inhibit compiler warnings */
    printf( "Winsock initialized...\n" );


    init_hints( &my_data ); /* Setup our preferences */
    get_host_info( "www.yahoo.com", "http", &my_data ); /* Get information about the host */
    connect_to_host( &my_data ); /* Connect to the host with the information we got earlier */


    /* Clean up */
    closesocket( my_data.socket );
    freeaddrinfo( my_data.server_info );


    free_winsock( );
    printf( "Program exited normally!\n" );


    return 0;
}

Connecting to it using http protocol works without any problems... :

Code:

Winsock initialized...
Connected to host!
Program exited normally!

I haven't been able to connect using smtp. I researched and found that most people said yahoo's smtp server is "smtp.mail.yahoo.com", but I tried that and I got error code 10060 ( connection timeout ). There might be a problem since I don't know how to use SSL encryption which is apparently required by yahoo, but I have no idea where the true problem lies. Any help connecting to smtp servers is appreciated.