你的朋友和你在同一个网络上吗？这个错误消息通常是当防火墙阻止通信时得到的错误消息。

Is your friend on the same network as you? This error message is typically one that you get when a firewall is preventing communication.

如果您的朋友和服务器之间没有防火墙，那么它也可以是防火墙或者服务器被配置为仅接受某些类型的连接（这对于服务器来说是非常正常的）。您能告诉我们有关您的服务器以及配置方式吗？

If there are no firewalls between your friend and the server, then it could also be a firewall on the server, or that the server is configured only to accept certain kinds of connections (which is very normal for a server). Can you tell us anything about your server and how it is configured?