How to resolve the 'connect: 43, could not connect to server' error in libetpan when connecting to different IMAP servers using C?

Question

when I run the imap-sample code of the libetpan library for C which is located in the tests directory of the github of the library https://github.com/dinhvh/libetpan, I get the error: connect: 43 could not connect to server what is the problem ?

#include <libetpan/libetpan.h>
#include <stdlib.h>
#include <sys/stat.h>

static void check_error(int r, char * msg)
{
    if (r == MAILIMAP_NO_ERROR)
        return;
  if (r == MAILIMAP_NO_ERROR_AUTHENTICATED)
        return;
  if (r == MAILIMAP_NO_ERROR_NON_AUTHENTICATED)
        return;
    
    fprintf(stderr, "%s\n", msg);
    exit(EXIT_FAILURE);
}

static char * get_msg_att_msg_content(struct mailimap_msg_att * msg_att, size_t * p_msg_size)
{
    clistiter * cur;
    
  /* iterate on each result of one given message */
    for(cur = clist_begin(msg_att->att_list) ; cur != NULL ; cur = clist_next(cur)) {
        struct mailimap_msg_att_item * item;
        
        item = clist_content(cur);
        if (item->att_type != MAILIMAP_MSG_ATT_ITEM_STATIC) {
            continue;
        }
        
    if (item->att_data.att_static->att_type != MAILIMAP_MSG_ATT_BODY_SECTION) {
            continue;
    }
        
        * p_msg_size = item->att_data.att_static->att_data.att_body_section->sec_length;
        return item->att_data.att_static->att_data.att_body_section->sec_body_part;
    }
    
    return NULL;
}

static char * get_msg_content(clist * fetch_result, size_t * p_msg_size)
{
    clistiter * cur;
    
  /* for each message (there will be probably only on message) */
    for(cur = clist_begin(fetch_result) ; cur != NULL ; cur = clist_next(cur)) {
        struct mailimap_msg_att * msg_att;
        size_t msg_size;
        char * msg_content;
        
        msg_att = clist_content(cur);
        msg_content = get_msg_att_msg_content(msg_att, &msg_size);
        if (msg_content == NULL) {
            continue;
        }
        
        * p_msg_size = msg_size;
        return msg_content;
    }
    
    return NULL;
}

static void fetch_msg(struct mailimap * imap, uint32_t uid)
{
    struct mailimap_set * set;
    struct mailimap_section * section;
    char filename[512];
    size_t msg_len;
    char * msg_content;
    FILE * f;
    struct mailimap_fetch_type * fetch_type;
    struct mailimap_fetch_att * fetch_att;
    int r;
    clist * fetch_result;
    struct stat stat_info;
    
    snprintf(filename, sizeof(filename), "download/%u.eml", (unsigned int) uid);
    r = stat(filename, &stat_info);
    if (r == 0) {
        // already cached
        printf("%u is already fetched\n", (unsigned int) uid);
        return;
    }
    
    set = mailimap_set_new_single(uid);
    fetch_type = mailimap_fetch_type_new_fetch_att_list_empty();
    section = mailimap_section_new(NULL);
    fetch_att = mailimap_fetch_att_new_body_peek_section(section);
    mailimap_fetch_type_new_fetch_att_list_add(fetch_type, fetch_att);

    r = mailimap_uid_fetch(imap, set, fetch_type, &fetch_result);
    check_error(r, "could not fetch");
    printf("fetch %u\n", (unsigned int) uid);
    
    msg_content = get_msg_content(fetch_result, &msg_len);
    if (msg_content == NULL) {
        fprintf(stderr, "no content\n");
        mailimap_fetch_list_free(fetch_result);
        return;
    }
    
    f = fopen(filename, "w");
    if (f == NULL) {
        fprintf(stderr, "could not write\n");
        mailimap_fetch_list_free(fetch_result);
        return;
    }
    
    fwrite(msg_content, 1, msg_len, f);
    fclose(f);
    
    printf("%u has been fetched\n", (unsigned int) uid);
    
    mailimap_fetch_list_free(fetch_result);
}

static uint32_t get_uid(struct mailimap_msg_att * msg_att)
{
    clistiter * cur;
    
  /* iterate on each result of one given message */
    for(cur = clist_begin(msg_att->att_list) ; cur != NULL ; cur = clist_next(cur)) {
        struct mailimap_msg_att_item * item;
        
        item = clist_content(cur);
        if (item->att_type != MAILIMAP_MSG_ATT_ITEM_STATIC) {
            continue;
        }
        
        if (item->att_data.att_static->att_type != MAILIMAP_MSG_ATT_UID) {
            continue;
        }
        
        return item->att_data.att_static->att_data.att_uid;
    }
    
    return 0;
}

static void fetch_messages(struct mailimap * imap)
{
    struct mailimap_set * set;
    struct mailimap_fetch_type * fetch_type;
    struct mailimap_fetch_att * fetch_att;
    clist * fetch_result;
    clistiter * cur;
    int r;
    
    /* as improvement UIDVALIDITY should be read and the message cache should be cleaned
       if the UIDVALIDITY is not the same */
    
    set = mailimap_set_new_interval(1, 0); /* fetch in interval 1:* */
    fetch_type = mailimap_fetch_type_new_fetch_att_list_empty();
    fetch_att = mailimap_fetch_att_new_uid();
    mailimap_fetch_type_new_fetch_att_list_add(fetch_type, fetch_att);

    r = mailimap_fetch(imap, set, fetch_type, &fetch_result);
    check_error(r, "could not fetch");
    
  /* for each message */
    for(cur = clist_begin(fetch_result) ; cur != NULL ; cur = clist_next(cur)) {
        struct mailimap_msg_att * msg_att;
        uint32_t uid;
        
        msg_att = clist_content(cur);
        uid = get_uid(msg_att);
        if (uid == 0)
            continue;

        fetch_msg(imap, uid);
    }

    mailimap_fetch_list_free(fetch_result);
}

int main(int argc, char ** argv)
{
    struct mailimap * imap;
    int r;
    
    /*
    ./imap-sample [email protected] mygmailpassword
    */
    if (argc < 3) {
        fprintf(stderr, "usage: imap-sample [gmail-email-address] [password]\n");
        exit(EXIT_FAILURE);
    }
    
    mkdir("download", 0700);
    
    imap = mailimap_new(0, NULL);
    r = mailimap_ssl_connect(imap, "imap.mail.yahoo.com", 993);
    fprintf(stderr, "connect: %i\n", r);
    check_error(r, "could not connect to server");
    
    r = mailimap_login(imap, argv[1], argv[2]);
    check_error(r, "could not login");
    
    r = mailimap_select(imap, "INBOX");
    check_error(r, "could not select INBOX");
    
    fetch_messages(imap);
    
    mailimap_logout(imap);
    mailimap_free(imap);
    
    exit(EXIT_SUCCESS);
}

for the record I changed the imap server to outlook and yahoo and it still does not work and the username and password I give to the program when running it as a command line argument is correct ! and I can connect to the imap server of google with my login info using curl so the server is alright!