1. 從檔案中讀

        string szFileName = "../ClientLog.txt";
        fstream input(szFileName, ios::in | ios::binary);
        msg.ParseFromIstream(&input);
        output.close();

2. 寫入檔案

    string szFileName = "../ClientLog.txt";
    fstream output(szFileName, ios::out | ios::binary |ios::app);
    msg.SerializePartialToOstream(&output)
    output.close();