NGINX提供502坏网关但在Ubnatu 14.04上与Apache2一起正常工作

Question

php5 over nginx正在提供502坏网关，但在apache2.Am正常运行Apache默认端口和nginx端口81上工作正常。

错误日志消息：

2016/12/02 12:32:05 [alert] 10119#0: 768 worker_connections are not enough
2016/12/02 12:32:05 [error] 10119#0: *2295 recv() failed (104: Connection reset by peer) while 
reading response header from upstream, client: 127.0.0.1, server: localhost, request: 
"GET /index.php HTTP/1.0", upstream: "http://127.0.0.1:81/index.php", host: "127.0.0.1".

我的自定义服务器文件：

server {
    listen   81;
    root /var/www/html/laralvelproj/public/;
    index index.html index.htm index.php;

    server_name localhost;
    error_log  /var/www/html/yoyogrx.com-error.log error;
    location / {
            try_files $uri $uri/ /index.php?$query_string;
    }
    location ~ \.php$ {

    proxy_set_header X-Real-IP  $remote_addr;
    proxy_set_header X-Forwarded-For $remote_addr;
    proxy_set_header Host $host;
    proxy_pass http://127.0.0.1:81;
     }
}

有人可以帮助我。