参考：
https://new.qq.com/rain/a/20231013A03U0A00

centos安装nginx

yum -y install nginx 

CentOS系统中Nginx的默认安装目录为/etc/nginx。

如果需要修改Nginx的配置文件，可以使用vi或者nano等编辑器打开该目录下的nginx.conf文件进行编辑。

示例代码（在命令行中输入）

vim /etc/nginx/nginx.conf

启动、停止、重启Nginx服务

systemctl start nginx   # 启动Nginx
systemctl stop nginx    # 停止Nginx
systemctl restart nginx # 重启Nginx

nginx 日志

/var/log/nginx/error.log 
/var/log/nginx/access.log

配置websocket

vim /etc/nginx/nginx.conf
配置文件如下：

# For more information on configuration, see:
#   * Official English Documentation: http://nginx.org/en/docs/
#   * Official Russian Documentation: http://nginx.org/ru/docs/

user root;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

# Load dynamic modules. See /usr/share/doc/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;

events {
    worker_connections 1024;
}

http {
    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  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 2048;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;


map $http_upgrade $connection_upgrade {
    default upgrade;
    '' close;
}

upstream wsbackend{
    server 192.168.17.188:9005;
    server 192.168.17.188:9006;
    keepalive 1000;
}

    server {
        listen       8009 default_server;
        #listen       [::]:80 default_server;
        server_name  localhost;
        root         /usr/share/nginx/html;

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        location / {
      proxy_pass http://wsbackend; 
          proxy_http_version 1.1;
          proxy_read_timeout   3600s; # 超时设置
          # 启用支持websocket连接
          proxy_set_header Upgrade $http_upgrade;
          proxy_set_header Connection "upgrade";
        }

        error_page 404 /404.html;
            location = /40x.html {
        }

        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }
    }

# Settings for a TLS enabled server.
#
#    server {
#        listen       443 ssl http2 default_server;
#        listen       [::]:443 ssl http2 default_server;
#        server_name  _;
#        root         /usr/share/nginx/html;
#
#        ssl_certificate "/etc/pki/nginx/server.crt";
#        ssl_certificate_key "/etc/pki/nginx/private/server.key";
#        ssl_session_cache shared:SSL:1m;
#        ssl_session_timeout  10m;
#        ssl_ciphers PROFILE=SYSTEM;
#        ssl_prefer_server_ciphers on;
#
#        # Load configuration files for the default server block.
#        include /etc/nginx/default.d/*.conf;
#
#        location / {
#        }
#
#        error_page 404 /404.html;
#            location = /40x.html {
#        }
#
#        error_page 500 502 503 504 /50x.html;
#            location = /50x.html {
#        }
#    }

}

重要的是这两行，它表明是websocket连接进入的时候，进行一个连接升级将http连接变成websocket的连接。

proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";

proxy_read_timeout; 表明连接成功以后等待服务器响应的时候，如果不配置默认为60s；
proxy_http_version 1.1; 表明使用http版本为1.1

遇到的问题：

2023/12/18 10:59:30 [crit] 626773#0: *1 connect() to :9006 failed (13: Permission denied) while connecting to upstream, client: , server: localhost, request: "GET / HTTP/1.1", upstream: "http://192:9006/", host: ":8009

解决办法：
1.nginx.conf的 开头改为：user root;
2.关闭SeLinux
临时关闭（不用重启机器）

setenforce 0 

参考：
https://www.jianshu.com/p/6205c8769e3c
https://blog.csdn.net/lazycheerup/article/details/117323466