このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
putty error
対処
関連リンク
Unable to connect to amazon EC2 instance via PuTTY - Stack Overflow
https://stackoverflow.com/questions/33125410/unable-to-connect-to-amazon-ec2-instance-via-putty
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https://stackoverflow.com/questions/15918407/network-error-connection-refused-putty-error
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https://www.youtube.com/watch?v=yaO0PLWbaLQ
https://www.youtube.com/watch?v=yaO0PLWbaLQ
PuTTY fatal Error - Connection Refused - Super User
https://superuser.com/questions/1185683/putty-fatal-error-connection-refused
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https://superuser.com/questions/1084283/network-error-connection-timed-out-while-ssh-aws-ec2-ubuntu-・・・
linux - SSH Network Error: Software caused ...
https://superuser.com/questions/1083783/ssh-network-error-software-caused-connection-abort