我正在尝试使用 ssh 连接到服务器，昨天它运行正常。但是今天它失败了，当我尝试使用 进行测试时ssh localhost，它成功了。以下是失败的输出：
OpenSSH_8.2p1 Ubuntu-4ubuntu0.5, OpenSSL 1.1.1f 31 Mar 2020
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: Connecting to boa-cheng.duckdns.org [155.33.213.0] port 22.
debug1: connect to address 155.33.213.0 port 22: Connection refused
ssh: connect to host boa-cheng.duckdns.org port 22: Connection refused
有人可以给出一些建议吗？我非常感谢您的帮助。