关于nginx返现代理统配配置

[S925379638]

是这样的，我希望当访问s1.test.com时自动跳转到 http://127.0.0.1:15501/ 当访问s2.test.com时跳转到http://127.0.0.1:15502/;
后面的端口尾号始终取s后面的数值 应该怎么配置呢 求大神帮助哈，谢谢
server {
listen 80;
server_name s1.test.com;
location /
{
proxy_set_header Host $host;
proxy_set_header X-Real-Ip $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_pass http://127.0.0.1:15501/;
}
}

server {
listen 80;
server_name s2.test.com;;
location /
{
proxy_set_header Host $host;
proxy_set_header X-Real-Ip $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_pass http://127.0.0.1:15502/;