2

我正在尝试使用下面的代码连接到 UDP 跟踪器服务器，但我没有收到来自跟踪器的任何响应...

我从这个链接中收集了我能做到的：http: //xbtt.sourceforge.net/udp_tracker_protocol.html

我以为我明白了……但显然没有。代码执行良好，然后在调用 RecvFrom 时挂起。所以我猜我要么没有发送正确的数据，要么我将它发送到错误的地方......

struct ConnectionIdRequest_t {

    uint64_t connectionId;
    uint32_t action;
    int32_t transactionId;
} typedef ConnectionIdRequest;

const bool UdpTorrentTrackerComm::initiateConnection(const int amountUploaded, 
const int amountDownloaded, 
const int amountLeft) {

    struct sockaddr_in serverAddress, clientAddress;
    struct hostent * host;
    struct in_addr address;

    //Setup dummy client address
    clientAddress.sin_family = AF_INET;
    clientAddress.sin_addr.s_addr = htonl(INADDR_ANY);
    clientAddress.sin_port = htons(0);

    //Setup server address
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_port = htons(portNumber);

    //SETUP in_addr server address
    //If we have an IP
    if (trackerAddress) {

        if (isIp4Address(*trackerAddress)) {

            //retrieve hostname from ip address 
            if (inet_aton(trackerAddress->c_str(), &address)) {

                host = gethostbyaddr((const char *) &address, sizeof(address), AF_INET);
                trackerHostname = new std::string(host->h_name);
            }
            else {
                return false;
            }
        }
        else {
            return false;
        }
    }
    else {
        //retrieve ip address from hostname
        host = gethostbyname(trackerHostname->c_str());
        address.s_addr = ((struct in_addr *) host->h_addr_list)->s_addr;
        trackerAddress = new std::string(inet_ntoa(address));
    }
std::cout << *trackerAddress << std::endl;
    //Convert trackerAddress to network format
    if(!inet_aton(trackerAddress->c_str(), &serverAddress.sin_addr)) {
        return false;
    }

    int sockFd = -1;
    //Add IPv6 in the future
    if ((sockFd = Socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        return false;
    }

    //Bind my address to the socket
    if (Bind(sockFd, (struct sockaddr *) &clientAddress, sizeof(clientAddress)) == - 1) {
        return false;
    }

    std::cout << "SendTo\n";
    ConnectionIdRequest * idRequest = createConnectionIdRequest();
    if (SendTo(sockFd, idRequest, sizeof(*idRequest), 0, 
        (struct sockaddr *) &serverAddress, sizeof(serverAddress)) == -1) {
        return false;
    }
    timeRequestSent = clock();
std::cout << "Sent: " << idRequest->connectionId << "|||" << idRequest->action << "|||" << idRequest->transactionId << std::endl;
    std::cout << "RecvFrom\n";
    char buffer[3000];
    socklen_t serverAddressLength = sizeof(serverAddress);
    while(true) {
        if (RecvFrom(sockFd, buffer, 3000, 0, 
            (struct sockaddr *) &serverAddress, &serverAddressLength) == - 1) {
            break;
            std::cout << "breaking...\n";
        }
    }
    std::cout << "The buffer is: " << buffer << std::endl;
    Close(sockFd);

    return true;
}

ConnectionIdRequest * UdpTorrentTrackerComm::createConnectionIdRequest() {

    ConnectionIdRequest * idRequest = new ConnectionIdRequest;
    generatePeerId();
    idRequest->connectionId = htonll(0x41727101980);
    idRequest->action = htonl(CONNECT);
    idRequest->transactionId = htonl(*peerId);

    return idRequest;
}

编辑：好吧，我做了 Arvid 建议的一项更改，但这没有任何帮助。我正在检查并确保我将所有正在发送的字节都转换为网络字节顺序......也许我错过了一些东西......

4

2 回答 2

1

看起来您将事务 ID 和对等 ID 混为一谈。它们是不同的。事务 ID 是您发送的 cookie，以便将返回的数据包与正确的请求相匹配。

看起来您还没有初始化 connectionID。您必须在初始连接消息中将其设置为神奇的 64 位数字。0x41727101980

您可以在此处找到替代协议描述。

于 2013-10-02T01:22:02.490 回答
1

我最终让它工作。问题主要是我没有转换所有需要转换为大端（网络排序）的值，以及使用过时的函数（gethostbyname 等）。

如果您想了解更多详细信息，请发表评论。

这是适用于我与跟踪器服务器建立链接的代码：

注意： serverAddress 和 clientAddress 是类型字段：struct sockaddr_in

const bool UdpTorrentTrackerComm::initiateConnection() {

    //Setup dummy client address
    clientAddress.sin_family = AF_INET;
    clientAddress.sin_addr.s_addr = htonl(INADDR_ANY);
    clientAddress.sin_port = htons(51413);

    //Setup server address
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_port = htons(portNumber);

    //SETUP in_addr server address
    //If we have an IP
    if (trackerAddress) {

        if (isIp4Address(*trackerAddress)) {

            //Convert human readable trackerAddress to network byte order ip address and place in serverAddress.sin_addr
            if (inet_pton(AF_INET, trackerAddress->c_str(), &(serverAddress.sin_addr))) {

                //retrieve hostname and service type from ip address        
                char hostBuffer[100], serviceBuffer[100];
                getnameinfo((struct sockaddr *) &serverAddress, sizeof(serverAddress), 
                    hostBuffer, sizeof(hostBuffer), 
                    serviceBuffer, sizeof(serviceBuffer), 
                    NI_NAMEREQD | NI_DGRAM);

                trackerHostname = new std::string(hostBuffer);
            }
            else {
                return false;
            }
        }
        else {
            return false;
        }
    }
    else {

        //Setup structs to be used in getaddrinfo
        struct addrinfo hints;
        struct addrinfo * result, * resultPointer;
        hints.ai_family = AF_INET;
        hints.ai_socktype = SOCK_DGRAM;
        hints.ai_flags = 0;
        hints.ai_protocol = 0;

        //Convert port number to string to pass to getaddrinfo
        std::stringstream ss;
        ss << portNumber;
        std::string portNumberString = ss.str();

        //retrieve ip address from hostname--------
        if (GetAddrInfo(trackerHostname->c_str(), portNumberString.c_str(), &hints, &result) != 0) {
            return false;
        }

        //Iterate over results for IP address V4 (ADD V6 later!)
        char ipBuffer[INET_ADDRSTRLEN];
        for (resultPointer = result; resultPointer != NULL; resultPointer = resultPointer->ai_next) {

            //If we have an IPv4 address
            if (resultPointer->ai_family == AF_INET) {

                //convert to presentation format and store in ipBuffer
                inet_ntop(AF_INET, &((struct sockaddr_in *) resultPointer->ai_addr)->sin_addr, ipBuffer, INET_ADDRSTRLEN);
            }
        }
        //Free result
        freeaddrinfo(result);

        //Convert ipBuffer to std::string and store in trackerAddress field
        trackerAddress = new std::string(ipBuffer);

        //Convert trackerAddress to network format
        if(!inet_pton(AF_INET, trackerAddress->c_str(), &serverAddress.sin_addr)) {
            return false;
        }

    }

    int sockFd = -1;
    //Add IPv6 in the future
    if ((sockFd = Socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        return false;
    }

    //Bind my address to the socket
    if (Bind(sockFd, (struct sockaddr *) &clientAddress, sizeof(clientAddress)) == - 1) {
        return false;
    }

    //Send a request to the tracker
    ConnectionIdRequest * idRequest = createConnectionIdRequest();
    if (SendTo(sockFd, idRequest, sizeof(*idRequest), 0, 
        (struct sockaddr *) &serverAddress, sizeof(serverAddress)) == -1) {
        return false;
    }
    timeRequestSent = clock();

    //Re-send until timeout.....
    ConnectionIdResponse idResponse;
    socklen_t serverAddressLength = sizeof(serverAddress);
    while((timeRequestSent - clock()) / 1000 < SECONDS_UNTIL_TIMEOUT) {

        //Response received!
        if (RecvFrom(sockFd, &idResponse, sizeof(idResponse), 0, 
            (struct sockaddr *) &serverAddress, &serverAddressLength) > 0) {
            break;
        }
    }

    //Set class fields that will persist
    activeSocket = sockFd;
    connectionId = ntohll(idResponse.connectionId);

    delete idRequest;

    return true;
}

其中 ConnectionIdResponse 和 ConnectionIdRequest 这两个结构定义为：

    /* Struct used to send a request for a connectionId to the tracker server.*/
struct ConnectionIdRequest_t {

    uint64_t connectionId;
    uint32_t action;
    uint32_t transactionId;
} typedef ConnectionIdRequest;

/* Struct used in receipt of a request for a connectionId from the tracker server. */
struct ConnectionIdResponse_t {
    uint32_t action;
    uint32_t transactionId;
    uint64_t connectionId;
} typedef ConnectionIdResponse;
于 2013-10-06T01:48:37.147 回答