c# - “主动拒绝连接”和“一段时间后没有正确响应”之间的区别

Question

当 Windows.Networking.Sockets.StreamSocket 类的 ConnectAsync 方法失败时，我得到 2 类错误。

“连接尝试失败，因为连接方在一段时间后没有正确响应，或者连接失败，因为连接的主机没有响应。”

或者

“无法建立连接，因为目标机器主动拒绝它”

这两个错误都是随机发生的，因此我无法弄清楚两者之间的区别。这些之间的技术区别是什么？

Answer 1

• The former usually means that the target machine is inaccessible (e.g. it's off, or your internet connection is down, etc.)
• The latter means the machine has been reached, but the TCP port is not open (usually it means that the server program is not running; there is no socket listening on it).

Note that if the target machine is running a firewall application that blocks this port, it's usually configured to pretend the machine is inaccessible (by silently dropping all connection requests) instead of actively refusing the connection.