ssh 提示Connection closed by * 的解决方案

 # 出现问题的机器执行
 [root@localhost ~]# service sshd restart
 
 # 其他机器链接过去，只能连接一次就接着会报错
 [root@localhost ~]# ssh root@172.17.0.84
 The authenticity of host '172.17.0.84 (172.17.0.84)'can't be established.
 RSA key fingerprint is f7:ce:40:fd:7c:d5:c8:64:2a:b9:bb:00:42:6b:25:9f.
 Are you sure you want to continue connecting (yes/no)? 

 [root@localhost ~] sshroot@172.17.0.84
 Connection closed by 172.17.0.84 port 22
 [root@localhost ~] sshroot@172.17.0.84
 Connection closed by 172.17.0.84 port 22
 [root@localhost ~] sshroot@172.17.0.84
 Connection closed by 172.17.0.84 port 22

 [root@localhost ~]# nc -w 1 172.17.0.84 22 < /dev/null && echo "tcp port ok"
 SSH-2.0-OpenSSH_5.3
 tcp port ok

 [root@localhost ~]# service iptables status
 iptables: Firewall is not running.

 [root@localhost ~]# vim /var/log/messages
 Jan 1511:24:53 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:57 localhost sshd[1740]: error: Could not load host key: /etc/ssh/ssh_host_rsa_key
 Jan 1511:24:57 localhost sshd[1740]: error: Could not load host key: /etc/ssh/ssh_host_dsa_key
 Jan 1511:24:58 localhost kernel: __ratelimit: 14450callbacks suppressed
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:24:58 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:01 localhost sshd[1744]: error: Could not load host key: /etc/ssh/ssh_host_rsa_key
 Jan 1511:25:01 localhost sshd[1744]: error: Could not load host key: /etc/ssh/ssh_host_dsa_key
 Jan 1511:25:03 localhost kernel: __ratelimit: 14573callbacks suppressed
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:03 localhost kernel: TCP: time wait bucket table overflow
 Jan 1511:25:05 localhost kernel: atkbd.c: Unknown key pressed (translated set2, code 0x0 on isa0060/serio0).
 Jan 1511:25:05 localhost kernel: atkbd.c: Use 'setkeycodes 00 <keycode>'to makeit known.
 Jan 1511:25:05 localhost kernel: atkbd.c: Unknown key released (translated set2, code 0x0 on isa0060/serio0).
 Jan 1511:25:05 localhost kernel: atkbd.c: Use 'setkeycodes 00 <keycode>'to makeit known.
 Jan 1511:25:08 localhost kernel: __ratelimit: 14688callbacks suppressed

 [root@localhost ssh]# ls -Zd *
 -rw-------. root root system_u:object_r:etc_t:s0       moduli
 -rw-r--r--. root root system_u:object_r:etc_t:s0       ssh_config
 -rw-------root root ?                               sshd_config
 -rw-------root root ?                               ssh_host_dsa_key
 -rw-r--r--root root ?                               ssh_host_dsa_key.pub
 -rw-------root root ?                               ssh_host_key
 -rw-r--r--root root ?                               ssh_host_key.pub
 -rw-------root root ?                               ssh_host_rsa_key
 -rw-r--r--root root ?                               ssh_host_rsa_key.pub