Nginx1.15.2代理TCP无法获取响应数据

Question

请求8787和8789的端口不能获取响应数据，但是直接请求8788的端口可以获取响应数据。这是我的Nginx的配置。

#user  nobody;
worker_processes  10;
#error_log  logs/error.log;
#error_log  logs/error.log  notice;
error_log   /usr/local/var/log/nginx/error.log  debug;
#pid        logs/nginx.pid;
events {
    worker_connections  1024;
}

stream {
    server{
        listen 8787;
        proxy_pass gintest;
    }

    upstream gintest{
        server localhost:8788;
    }
    server{
        listen 8789;
        proxy_buffer_size 16k;
        proxy_pass 127.0.0.1:8788;
    }
}