Nginx+uWSGI+Flask 配置失败，求教

from flask import Flask

app = Flask(__name__)

@app.route("/")
def index():
    return("Hello world")

@app.route("/about")
def about():
    return("this is a test")

if __name__ == "__main__":
    app.run()

[uwsgi]
# uwsgi 启动时所使用的地址与端口
socket = 127.0.0.1:3031
chdir = /home/www/app
wsgi-file = app.py
callable = app
# 处理器数
processes = 4
# 线程数
threads = 2
#状态检测地址
stats = 127.0.0.1:9191
#守护进程
daemonize = /var/log/uwsgi/uwsgi.log

events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  logs/access.log  main;
    sendfile        on;
    keepalive_timeout  65;

    server {
        listen       80;
        server_name  127.0.0.1;

        #charset koi8-r;

        access_log  logs/host.access.log  main;

        location / {
            include uwsgi_params;
            uwsgi_pass 127.0.0.1:3031;
        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html
        #
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}