Question

我必须通过套接字从Internet下载文件。我写了这段代码，结果有点奇怪。当我编译它并运行它只是创建sample.mp3（它是空的）。如果我用调试器运行它，它会创建文件并填充一点（274 720字节）。我该如何解决？我正在使用带有mingw32 compilator的Code :: Blocks。

#include <iostream>
#include <winsock2.h>
#include <string>
#include <fstream>

#define DEFAULT_BUFFLEN 1024

using namespace std;

int main()
{
    char* host;
    char* req;

    host = "cs9-5v4.vk.me";
    req = "/p18/f854bad2afcb34.mp3?extra=KOpJtWM9maWNBYyDfiQwKFo6p6cZ_EfQz4O_Jzz26anBd9bPXYlqageCjJQe5yNqfnaGAXKtP5jwQYWf1CaTef9dJomPrzya";

    string rdyStr;
    rdyStr += "GET ";
    rdyStr += req;
    rdyStr += " HTTP/1.1\nHost: ";
    rdyStr += host;
    rdyStr += "\n\n";

    WSADATA wsaData;
    WORD version;
    int error;

    version = MAKEWORD( 2, 0);

    error = WSAStartup( version, &wsaData );

    if (error != 0)
    {
        cout << "There is some error:" << error << endl;
        return -1;
    }

    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 0)
    {
        WSACleanup();
        cout << "Incorrect winsock version" << endl;
        return -2;
    }

    SOCKET client;

    client = socket(AF_INET, SOCK_STREAM, 0);

    struct hostent *Host;

    Host = gethostbyname( host );

    if (Host == NULL)
    {
        cout << "There is no such host" << endl;
        return -3;
    }

    struct sockaddr_in sin;

    memset(&sin, 0, sizeof(sin));

    sin.sin_family = AF_INET;
    sin.sin_port = htons(80);
    sin.sin_addr.s_addr = ((struct in_addr *)(Host->h_addr))->s_addr;

    if (connect(client, (struct sockaddr *) &sin, sizeof(sin)) == SOCKET_ERROR)
    {
        cout << "Cant connect to the server" << endl;
        return -4;
    }

    char result[DEFAULT_BUFFLEN];
    int recvResult = 1;
    int recvBufflen = DEFAULT_BUFFLEN;

    int rs = send(client, rdyStr.c_str(), recvBufflen, 0);
    rs = shutdown(client, SD_SEND);

    ofstream fl;
    fl.open("sample.mp3", ios::out | ios::binary);
    getchar();
    do
    {
        recvResult = recv(client, result, recvBufflen, 0);
        fl.write(result, recvResult);

        if (recvResult < 0)
        {
            cout << "There is some errors with reciecing info" << endl;
            return -5;
        }
    }
    while (recvResult > 0);

    fl.close();
}

Answer 1

在之后你已经测试了read（）结果为零或负数之前，你不应该调用write（）。您可以将循环写为：

while ((recvCount = recv(client, result, recvBufLen, 0)) > 0) { fl.write(result, recvResult); }

然后进行错误测试。注意如果得到否定结果，则应在某处打印WSAGetLastError（）值。

套接字请求不返回整个文件

1 个答案: