//! @brief Get logfile name published by GUI and open file to write.
bool serviceCallback(atrias_controllers::data_subscriber_srv::Request& req, atrias_controllers::data_subscriber_srv::Response& res) {
    if (req.isLogging) {
        ROS_INFO("logging");
        char buffer[256];   // Create buffer to store filename.

        if (req.logfilename == "") {   // If filename is unspecified, set one based on date and time.
            time_t curSeconds;
            curSeconds = time(NULL);
            struct tm *tInfo;
            tInfo = localtime(&curSeconds);
            sprintf(buffer, "%s/atrias_%0.2d%0.2d%0.2d_%0.2d%0.2d%0.2d.log", "/home/drl/atrias/drl-sim/atrias/log_files", tInfo->tm_year%100, tInfo->tm_mon+1, tInfo->tm_mday, tInfo->tm_hour, tInfo->tm_min, tInfo->tm_sec);
        }
        else {   // If filename is specified, use that as logfilename.
            sprintf(buffer, "%s", req.logfilename.c_str());
        }

        log_file_fp = fopen(buffer, "w");   // Open logfile.
        fprintf(log_file_fp, "-");   // Make sure the file exists.
        ROS_INFO("data_subscriber opened logfile at %s", buffer);
        res.logfilename = buffer;   // Respond with new logfilename.
        isLogging = true;   // data_subscriber should start logging.
    }
    else if (!req.isLogging) {
        ROS_INFO("not logging");
        if (log_file_fp != NULL) {   // Check if logfile is open because serviceCallback could be run if logfilename is set but isLogging is off.
            fclose(log_file_fp);
            ROS_INFO("data_subscriber closed logfile.");
        }
        res.logfilename = "";   // Respond with blank logfilename.
    }
    return true;
}