test.cpp

int main () {
    UDPSocket sock (9000);
    sock.joinGroup("239.0.1.1");

    const int PACK_SIZE = 4096;
    const int BUF_LEN = 65540;

    char buffer[BUF_LEN];
    while(true) {
        unsigned short sourcePort;
        std::string sourceAddress;

        int recvMsgSize = sock.recvFrom(buffer, BUF_LEN, sourceAddress, sourcePort);
        if (recvMsgSize == sizeof(uint64_t)) {
            uint64_t total_pack = reinterpret_cast<uint64_t*>(buffer)[0];

            std::unique_ptr<char[]> longbuf (new char[PACK_SIZE * total_pack]);
            for (int i = 0; i < total_pack; i++) {
                recvMsgSize = sock.recvFrom(buffer, BUF_LEN, sourceAddress, sourcePort);
                if (recvMsgSize != PACK_SIZE) {
                    break;
                }
                memcpy( & longbuf.get()[i * PACK_SIZE], buffer, PACK_SIZE);
            }
            if (recvMsgSize != PACK_SIZE) {
                continue;
            }

            cv::Mat rawData (1, PACK_SIZE * total_pack, CV_8UC1, longbuf.get());
            cv::Mat frame = imdecode(rawData, CV_LOAD_IMAGE_COLOR);

            cv::imshow("debug", frame);
            cv::waitKey(1);
        }
    }
}