Ubuntu 12.04中xshell链接报：Read from socket failed: Connection reset by peer 或者 Connection closed by foreign host.错误解决办法：
该问题出现的原因是/etc/ssh目录下的文件的熟悉被修改了，从新修改回原始状态即可：
cd /etc/ssh
sudo chmod 644 ./*
sudo chmod 600 ssh_host_dsa_key
sudo chmod 600 ssh_host_rsa_key
sudo chmod 755 .