centos7上的xrdp无法连接

我使用本指南guide在centos 7上安装了xrdp

  netstat -antup | grep xrdp
    tcp        0      0 127.0.0.1:3350          0.0.0.0:*               LISTEN      3096/xrdp-sesman
    tcp        0      0 0.0.0.0:3389            0.0.0.0:*               LISTEN      3097/xrdp

所以这意味着它可以工作，但当我尝试连接到xrdp时，登录后我看到：

login succesfful for display 10
VNC started connecting
VNC connecting to 127.0.0.1 5910
VNC error - problem connecting
some problem

xrdp的日志文件：

[20170505-20:56:42] [INFO ] A connection received from 127.0.0.1 port 33004
[20170505-20:56:43] [INFO ] ++ created session (access granted): username root, ip my_ip:13473 - socket: 12
[20170505-20:56:43] [INFO ] starting Xvnc session...
[20170505-20:56:43] [DEBUG] Closed socket 9 (AF_INET 0.0.0.0:5910)
[20170505-20:56:43] [DEBUG] Closed socket 9 (AF_INET 0.0.0.0:6010)
[20170505-20:56:43] [DEBUG] Closed socket 9 (AF_INET 0.0.0.0:6210)
[20170505-20:56:43] [DEBUG] Closed socket 8 (AF_INET 127.0.0.1:3350)
[20170505-20:56:43] [DEBUG] Closed socket 7 (AF_INET 127.0.0.1:3350)
[20170505-20:56:43] [DEBUG] Closed socket 8 (AF_INET 127.0.0.1:3350)
[20170505-20:56:43] [INFO ] Xvnc :10 -auth .Xauthority -geometry 3840x2048 -depth 24 -rfbauth /root/.vnc/sesman_root_passwd:10 -bs -nolisten tcp -localhost -dpi 96
[20170505-20:56:43] [CORE ] waiting for window manager (pid 3029) to exit
[20170505-20:56:43] [CORE ] window manager (pid 3029) did exit, cleaning up session
[20170505-20:56:43] [INFO ] ++ terminated session:  username root, display :10.0, session_pid 3028, ip ip_goes_here:13473 - socket: 12

我无法理解这背后的问题，有什么建议吗？