Nginx proxy_pass to Minecraft server

try this in your DNS records

A RECORD

Name     one.example.com
Value    <server_ip>
TTL  86400

Name     two.example.com
Value    <server_ip>
TTL  86400

---

SRV RECORD

Name     _minecraft._tcp.one.example.com
Port     25500
Value    one.example.com

Name     _minecraft._tcp.two.example.com
Port     25501
Value    two.example.com

As Dag Nabbit stated, a Minecraft server does not talk http. You would typically do this via NAT. A proxy server needs to know the protocol, because as the name suggests, it acts on behalf of the the client. Nginx knows various protocols, not just http, but Minecraft is not one of them. You can however write a proxy module for this protocol and use the existing nginx infrastructure. Since I'm not familiar with the protocol, I can't comment on the fact that this would have any advantages over NAT.