UPDATE: if I don\'t use socket and use 127.0.0.1:3031 instead, everything works fine.
127.0.0.1:3031
Nginx version is 1.6.3, and uwsgi is 2.0.11.1
Put the daimaduan_preview.ini's socket file into /run instead of /tmp. Like in this answer, your system probably using namespaced temporary directories, which means every service can only see its own files in /tmp.
daimaduan_preview.ini
/run
/tmp