需要配合nginx

location / {
    proxy_pass http://test; proxy_set_header Host $host:$server_port;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Real-PORT $remote_port;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

in node koa:

app.proxy = true;
ip = ctx.ip;