Libcurl為一個免費開源的，客戶端url傳輸庫，支持FTP，FTPS，TFTP，HTTP，HTTPS，GOPHER，TELNET，DICT，FILE和LDAP，跨平臺，支持Windows，Unix，Linux等，線程安全，支持Ipv6。并且易于使用。
http://curl.haxx.se/libcurl/
從http://curl.haxx.se/libcurl/ 下載一個穩定的版本，注意選擇OS。
在使用之前請大家多閱讀libcurl的文檔：因為如果要實際運用到項目中，最好對libcurl有具體的了解，具體在
http://curl.haxx.se/libcurl/c/
curl_easy_setopt()
curl_easy_perform()
curl_easy_getinfo()
這三個函數的使用上，需要多去鉆研，多看Samples，你才能靈活使用libcurl。
感謝這篇文章:
http://blog.163.com/xu_chao2000/blog/static/27770610200801303252802/
給了我許多啟發，再次感謝！
給出我的一個簡單的代碼例子：
說明:
1.PM...等參數，沒有具體意義，就是long,bool，int,char*等進行特殊封裝過，你可以用普通類型取代。
2.關鍵在curl_easy_setopt函數設置option,可以設置ftp,http,get,post等許多選項，請根據具體使用情況設置。
3.對取回來的數據需要進行判斷，比如http下載文件，如果文件不存在，需要進行處理。因為writer是可以將buf填充404 not found等網頁內容的，不能將這個內容當成文件內容，所以需要判斷http web返回來的code，進行判斷。
4.我有個問題，就是想得到服務器上filename的具體名稱，verbose調試已經返回了，但是我在getinfo的時候，試過好多選項，但未找到這個存放真實服務器文件名的選項，如果有知道的麻煩告訴我，謝謝了！
#include "curl/curl.h"
#pragma comment(lib, "libcurl.lib")
PM_ULONG writer(PM_VOID *data, PM_INT size, PM_INT nmemb, PmString &content);
PM_BOOL CurlInit(CURL *&curl, PM_LPCSTR url,PmString &content);
PM_BOOL GetURLDataBycurl(PM_LPCSTR URL, PmString &content);
void main()
{
//PM_LPSTR url="http://down1.chinaunix.net/distfiles/libpcap-1.0.20050129.tar.gz";
PM_LPCSTR url ="http://www.baidu.com/img/baidu.gif";
PmString content;
if ( GetURLDataBycurl(url,content))
{
printf("%s\n",content);
}
getchar();
}
PM_BOOL CurlInit(CURL *&curl, PM_LPCSTR url,PmString &content)
{
CURLcode code;
PmString error;
curl = curl_easy_init();
if (curl == NULL)
{
debug0( "Failed to create CURL connection\n");
return PM_FALSE;
}
code = curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, error);
if (code != CURLE_OK)
{
debug1( "Failed to set error buffer [%d]\n", code );
return PM_FALSE;
}
curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
code = curl_easy_setopt(curl, CURLOPT_URL, url);
if (code != CURLE_OK)
{
debug1("Failed to set URL [%s]\n", error);
return PM_FALSE;
}
code = curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
if (code != CURLE_OK)
{
debug1( "Failed to set redirect option [%s]\n", error );
return PM_FALSE;
}
code = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);
if (code != CURLE_OK)
{
debug1( "Failed to set writer [%s]\n", error);
return PM_FALSE;
}
code = curl_easy_setopt(curl, CURLOPT_WRITEDATA, &content);
if (code != CURLE_OK)
{
debug1( "Failed to set write data [%s]\n", error );
return PM_FALSE;
}
return PM_TRUE;
}
PM_ULONG writer(PM_VOID *data, PM_INT size, PM_INT nmemb, PmString &content)
{
PM_ULONG sizes = size * nmemb;
PmString temp(data,sizes);
content += temp;
return sizes;
}
PM_BOOL GetURLDataBycurl(PM_LPCSTR URL, PmString &content)
{
CURL *curl = NULL;
CURLcode code;
PmString error;
code = curl_global_init(CURL_GLOBAL_DEFAULT);
if (code != CURLE_OK)
{
debug1( "Failed to global init default [%d]\n", code );
return PM_FALSE;
}
if ( !CurlInit(curl,URL,content) )
{
debug0( "Failed to global init default [%d]\n" );
return PM_FALSE;
}
code = curl_easy_perform(curl);
if (code != CURLE_OK)
{
debug2( "Failed to get '%s' [%s]\n", URL, error);
return PM_FALSE;
}
PM_ULONG retcode = 0;
code = curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE , &retcode);
if ( (code == CURLE_OK) && retcode == 200 )
{
PM_DOUBLE length = 0;
code = curl_easy_getinfo(curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD , &length);
printf("%d",retcode);
FILE * file = fopen("1.gif","wb");
fseek(file,0,SEEK_SET);
fwrite(content.c_str(),1,length,file);
fclose(file);
//struct curl_slist *list;
//code = curl_easy_getinfo(curl,CURLINFO_COOKIELIST,&list);
//curl_slist_free_all (list);
return PM_TRUE;
}
else
{
// debug1( "%s \n ",getStatusCode(retcode));
return PM_FALSE;
}
curl_easy_cleanup(curl);
return PM_FALSE;
}