关于使用libcurl实现文件上传的一些困惑，请大家帮忙

2014-03-04 03:32:01 164 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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从Wireshark抓包看CURLOPT_POSTFIELDSIZE：为什么你设置的包大小和实际抓到的TCP包不一样？本文通过Wireshark抓包分析，揭示了`CURLOPT_POSTFIELDSIZE`设置与实际TCP包大小的差异原因。深入探讨了应用层与传输层的分包机制，包括MTU、MSS等关键概念，并提供了优化网络传输效率的实践方法，帮助开发者更好地理解网络编程中的抽象层次问题。阅读详情

为了实现文件上传到服务器我使用了以下代码：

 	curl_global_init(CURL_GLOBAL_ALL);

 	CURL* hCurl = curl_easy_init();

 	if(hCurl != NULL)

 	{

 		curl_slist* pOptionList = NULL;

 		int filesize=0;

		pOptionList = curl_slist_append(pOptionList, "Blog-X-User: username");

 		pOptionList = curl_slist_append(pOptionList, "Expect:");

 		curl_easy_setopt(hCurl, CURLOPT_HTTPHEADER, pOptionList);

 

 		curl_httppost* pFormPost = NULL;

 		curl_httppost* pLastElem = NULL;

 		//上传文件，指定本地文件完整路径

 		curl_formadd(&pFormPost, &pLastElem, CURLFORM_COPYNAME, "sendfile", CURLFORM_FILE, "D:\\a.png"/*, CURLFORM_CONTENTTYPE, "application/octet-stream"*/, CURLFORM_END);

 		curl_formadd(&pFormPost, &pLastElem, CURLFORM_COPYNAME, "filename", CURLFORM_COPYCONTENTS, "a.png", CURLFORM_END);

 		curl_formadd(&pFormPost,&pLastElem,CURLFORM_COPYNAME, "submit",CURLFORM_COPYCONTENTS, "send",



 		curl_easy_setopt(hCurl, CURLOPT_HTTPPOST, pFormPost);

 		curl_easy_setopt(hCurl, CURLOPT_URL, "http://XXXX.com/UploadFileServlet");

//  		curl_easy_setopt(hCurl, CURLOPT_HEADERFUNCTION,function);

 // 		curl_easy_setopt(hCurl, CURLOPT_FOLLOWLOCATION,1);

 // 		curl_easy_setopt(hCurl, CURLOPT_HEADERDATA, &filesize);

 

 		CURLcode res = curl_easy_perform(hCurl);

 

		double t=0;

		curl_easy_getinfo(hCurl,CURLINFO_SIZE_UPLOAD,&t); 



 		if(res != CURLE_OK)

 		{

 //			std::cout << "Error" << std::endl;

 		}

 

 		curl_formfree(pFormPost);

 		curl_easy_cleanup(hCurl);

 	}

 

 	curl_global_cleanup();