c++ - 如何解码跟踪器响应中的对等值 (Bittorrent)

Question

我正在尝试自己实现 bittorent 协议(protocol)，但我在使用 C++ 解码跟踪器响应中的“Peers”值时遇到问题。

根据bittorent协议(protocol)文档:

peers: (binary model) Instead of using the dictionary model described above, the peers value may be a string consisting of multiples of 6 bytes. First 4 bytes are the IP address and last 2 bytes are the port number. All in network (big endian) notation.

如何使用 C++ 解码这些 ip 和端口号？

我已经修改了这段代码，有点不正确:

void DecodePeers(OrderedMap<std::string, int> &map, const char * buffer, int i)
{
    int counter = 0;



    while (*(buffer + counter) != NULL)
    {

        //std::vector<TByte> portNum;
        short port;

        for (int i = counter; i < counter + 4; i++)
        {
            //*(peerIp + i - counter) = *(buffer + i);
        }

        counter += 4;

        //*(peerIp + 4) = '\0';
        char twobytes[2];

        twobytes[0] = *(buffer + counter + 0);
        twobytes[1] = *(buffer + counter + 1);

        unsigned int x;
        std::stringstream ss;
        ss << std::hex << twobytes[0];
        ss >> x;
        // output it as a signed type
        std::cout << static_cast<int>(x) << std::endl;

        port = ((twobytes[1] << 8) | twobytes[0]);
        //port = (short) twobytes;
        counter += 2;

        //std::string str(portNum.begin(), portNum.end());

        std::cout << std::endl;

        std::cout << port << std::endl ;

        char  * bbuffer = new char[100];

        for (int i = 0; i < 1; i++) {
            //unsigned int inte = (unsigned int)str;(
            //_itoa_s((int) *str.c_str(), bbuffer, 100, 10);
            //sprintf_s(bbuffer, 50, (const char *) "%d", str.c_str());
        }

        std::cout << std::endl;
        //int port = atoi(portNum);
        //map.Insert(str, port);
    }

}

有人知道如何将此数字转换为数字 - 可读响应吗？

Example of peers value: P^L♠*j.t╤u→πe199711

Answer 1

我试图在你的缓冲区上使用这段代码来解码 bittorrent 协议(protocol)对等体

#include <arpa/inet.h>

int main(int argc, char *argv[])
{
    char *buf = "P^L♠*j.t╤u→πe199711";
    int chunks = strlen(buf) / 6 ;
    int offset =  0;
    unsigned char *ip;
    unsigned short *port;
    int recsDone = 0;
    while (recsDone++ <= chunks){
        ip   = (unsigned char *) buf+offset;
        port = (unsigned short *) buf+offset+4;
        printf("%s - %d\n",inet_ntoa(*(in_addr*)ip),ntohs(*port));
        offset+=6;
    }
}

我得到这个作为输出:

80.94.76.226 - 1189242.106.46.116 - 12601

如果它有效，请告诉我们。