https://github.com/bitcoin/bitcoin/commit/2b781ad66e34000037f589c71366c203255ed058#r83655059
const Reply& reply = SendRequestAndGetReply(
            *sock,
            strprintf("SESSION CREATE STYLE=STREAM ID=%s DESTINATION=TRANSIENT", session_id));
        m_private_key = DecodeI2PBase64(reply.Get("DESTINATION"));
    } else {
        
        
        const auto& [read_ok, data] = ReadBinaryFile(m_private_key_file);
        if (read_ok) {
            m_private_key.assign(data.begin(), data.end());
        } else {
            GenerateAndSavePrivateKey(*sock);
        }
        const std::string& private_key_b64 = SwapBase64(EncodeBase64(m_private_key));
        SendRequestAndGetReply(*sock,
                               strprintf("SESSION CREATE STYLE=STREAM ID=%s DESTINATION=%s",
                                         session_id,
                                         private_key_b64));
    }
    m_my_addr = CService(DestBinToAddr(MyDestination()), I2P_SAM31_PORT);
    m_session_id = session_id;
    m_control_sock = std::move(sock);
    Log("%s SAM session %s created, my address=%s",
        Capitalize(session_type),
        m_session_id,
        m_my_addr.ToString());
}
std::unique_ptr<Sock> Session::StreamAccept()