我有一台运行 Ubuntu 16.04 Server 的台式计算机。它位于我的客厅，通过以太网线连接到路由器。 IP 地址是静态的 (192.168.50.249)，路由器上的 DHCP 配置为停止在 240。我在那里运行着一堆服务：PG 10.3、SSHd、Docker 和一些其他服务。我将它用于我的开发：我连接到服务器以使用 PG 和我在 docker 中运行的一些应用程序。我正在使用 MBP 进行工作，并通过 WiFi 从它连接到该服务器。
一段时间后（从几分钟到几天是不可预测的），应用程序级网络连接停止工作。我仍然可以 ping 服务器并 telnet 到任何端口，但实际上无法使用任何服务。对于 psql，它显示“服务器实际上正在侦听并侦听端口 5432”；对于 SSH，它返回“连接拒绝 192.168.50.249，端口 22”。
如果我远程登录到端口 22，它会连接，但在第一次按下按键后会退出并显示“协议不匹配”消息。
唯一有帮助的是服务器上的硬重置按钮。
如果我查看，/var/log/auth我看不到任何尝试连接的痕迹。成功的连接记录在那里。我尝试禁用密码连接（使用我的 RSA 密钥连接）并重新启用它，但没有帮助。看起来根本没有连接到 SSH 服务。我不是管理员，只是一个普通的 Linux 用户，我已经用尽了我有限的尝试清单。我还尝试检查防火墙是否正在运行（但没有）：
$ sudo service ufw status
● ufw.service - Uncomplicated firewall
Loaded: loaded (/lib/systemd/system/ufw.service; enabled; vendor preset: enabled)
Active: active (exited) since Tue 2018-03-20 13:11:26 CDT; 3h 38min ago
Process: 470 ExecStart=/lib/ufw/ufw-init start quiet (code=exited, status=0/SUCCESS)
Main PID: 470 (code=exited, status=0/SUCCESS)
Tasks: 0
Memory: 0B
CPU: 0
CGroup: /system.slice/ufw.service
$ sudo ufw status
Status: inactive
我也浏览过，/var/log/syslog但没有找到任何相关的内容。
请指出我要尝试的方向。
这也是 lspci 的输出：
00:00.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1450
00:00.2 IOMMU: Advanced Micro Devices, Inc. [AMD] Device 1451
00:01.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1452
00:01.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 1453
00:01.3 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 1453
00:02.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1452
00:03.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1452
00:04.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1452
00:07.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1452
00:07.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 1454
00:08.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1452
00:08.1 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 1454
00:14.0 SMBus: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller (rev 59)
00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge (rev 51)
00:18.0 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1460
00:18.1 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1461
00:18.2 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1462
00:18.3 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1463
00:18.4 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1464
00:18.5 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1465
00:18.6 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1466
00:18.7 Host bridge: Advanced Micro Devices, Inc. [AMD] Device 1467
01:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd Device a804
02:00.0 USB controller: Advanced Micro Devices, Inc. [AMD] Device 43bb (rev 02)
02:00.1 SATA controller: Advanced Micro Devices, Inc. [AMD] Device 43b7 (rev 02)
02:00.2 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43b2 (rev 02)
03:00.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43b4 (rev 02)
03:01.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43b4 (rev 02)
03:04.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43b4 (rev 02)
03:06.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43b4 (rev 02)
03:07.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] Device 43b4 (rev 02)
04:00.0 Ethernet controller: Intel Corporation I211 Gigabit Network Connection (rev 03)
09:00.0 Non-Essential Instrumentation [1300]: Advanced Micro Devices, Inc. [AMD] Device 145a
09:00.2 Encryption controller: Advanced Micro Devices, Inc. [AMD] Device 1456
09:00.3 USB controller: Advanced Micro Devices, Inc. [AMD] Device 145c
0a:00.0 Non-Essential Instrumentation [1300]: Advanced Micro Devices, Inc. [AMD] Device 1455
0a:00.2 SATA controller: Advanced Micro Devices, Inc. [AMD] FCH SATA Controller [AHCI mode] (rev 51)
0a:00.3 Audio device: Advanced Micro Devices, Inc. [AMD] Device 1457
和uname
$ uname -a Linux gladstone 4.4.0-116-generic #140-Ubuntu SMP Mon Feb 12 21:23:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
更新：
今天又发生了，我运行了 nmap：
sudo nmap -sS -A 192.168.50.249
Password:
Starting Nmap 7.70 ( https://nmap.org ) at 2018-04-04 07:55 CDT
Nmap scan report for gladstone (192.168.50.249)
Host is up (0.0021s latency).
Not shown: 999 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.4 (Ubuntu Linux; protocol 2.0)
MAC Address: 88:D7:F6:C4:F0:2B (Asustek Computer)
Device type: general purpose
Running: Linux 3.X|4.X
OS CPE: cpe:/o:linux:linux_kernel:3 cpe:/o:linux:linux_kernel:4
OS details: Linux 3.2 - 4.9
Network Distance: 1 hop
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
TRACEROUTE
HOP RTT ADDRESS
1 2.09 ms gladstone (192.168.50.249)
所以这是同一台计算机，可以通过 telnet 访问，但 SSH 不起作用。我被困住了。
远程登录工作原理：
telnet 192.168.50.249 22
Trying 192.168.50.249...
Connected to gladstone.
Escape character is '^]'.
SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
d
Protocol mismatch.
Connection closed by foreign host.
SSH 不工作：
ssh -vvv 192.168.50.249
OpenSSH_7.6p1, LibreSSL 2.6.2
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 48: Applying options for *
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.50.249 port 22.
debug1: Connection established.
debug1: identity file /Users/valentin/.ssh/id_rsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.4 pat OpenSSH* compat 0x04000000
debug3: fd 5 is O_NONBLOCK
debug1: Authenticating to 192.168.50.249:22 as 'valentin'
debug3: hostkeys_foreach: reading file "/Users/valentin/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/valentin/.ssh/known_hosts:37
debug3: load_hostkeys: loaded 1 keys from 192.168.50.249
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
Connection closed by 192.168.50.249 port 22
但是硬件重置后：
ssh -vvv 192.168.50.249
OpenSSH_7.6p1, LibreSSL 2.6.2
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 48: Applying options for *
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.50.249 port 22.
debug1: Connection established.
debug1: identity file /Users/valentin/.ssh/id_rsa type 0
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/valentin/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.4 pat OpenSSH* compat 0x04000000
debug3: fd 5 is O_NONBLOCK
debug1: Authenticating to 192.168.50.249:22 as 'valentin'
debug3: hostkeys_foreach: reading file "/Users/valentin/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/valentin/.ssh/known_hosts:37
debug3: load_hostkeys: loaded 1 keys from 192.168.50.249
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:L1h3Nhz+wvvg7SyJGUyNmMMSTPSXQ6URWv2xuCei3IU
debug3: hostkeys_foreach: reading file "/Users/valentin/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /Users/valentin/.ssh/known_hosts:37
debug3: load_hostkeys: loaded 1 keys from 192.168.50.249
debug1: Host '192.168.50.249' is known and matches the ECDSA host key.
debug1: Found key in /Users/valentin/.ssh/known_hosts:37
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /Users/valentin/.ssh/id_rsa (0x7f9cafc02be0)
debug2: key: /Users/valentin/.ssh/id_dsa (0x0)
debug2: key: /Users/valentin/.ssh/id_ecdsa (0x0)
debug2: key: /Users/valentin/.ssh/id_ed25519 (0x0)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:ZtUc3syi/EohVjwVTuqqvAYaLaDO58+yE6xXJ5iTOeg /Users/valentin/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg rsa-sha2-512 blen 535
debug2: input_userauth_pk_ok: fp SHA256:ZtUc3syi/EohVjwVTuqqvAYaLaDO58+yE6xXJ5iTOeg
debug3: sign_and_send_pubkey: RSA SHA256:ZtUc3syi/EohVjwVTuqqvAYaLaDO58+yE6xXJ5iTOeg
debug3: send packet: type 50
debug3: receive packet: type 52
debug1: Authentication succeeded (publickey).
Authenticated to 192.168.50.249 ([192.168.50.249]:22).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug3: receive packet: type 91
debug2: channel_input_open_confirmation: channel 0: callback start
debug2: fd 5 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x10
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug3: send packet: type 98
debug1: Sending environment.
debug3: Ignored env TMPDIR
debug3: Ignored env XPC_FLAGS
debug3: Ignored env Apple_PubSub_Socket_Render
debug3: Ignored env TERM
debug1: Sending env LANG = en_US.UTF-8
debug2: channel 0: request env confirm 0
debug3: send packet: type 98
debug3: Ignored env SSH_AUTH_SOCK
debug3: Ignored env SECURITYSESSIONID
debug3: Ignored env XPC_SERVICE_NAME
debug3: Ignored env TERM_PROGRAM
debug3: Ignored env TERM_PROGRAM_VERSION
debug3: Ignored env TERM_SESSION_ID
debug3: Ignored env SHELL
debug3: Ignored env HOME
debug3: Ignored env LOGNAME
debug3: Ignored env USER
debug3: Ignored env PATH
debug3: Ignored env SHLVL
debug3: Ignored env PWD
debug3: Ignored env OLDPWD
debug3: Ignored env ZSH
debug3: Ignored env PAGER
debug3: Ignored env LESS
debug1: Sending env LC_CTYPE = en_US.UTF-8
debug2: channel 0: request env confirm 0
debug3: send packet: type 98
debug3: Ignored env LSCOLORS
debug3: Ignored env RBENV_SHELL
debug3: Ignored env _
debug3: Ignored env __CF_USER_TEXT_ENCODING
debug2: channel 0: request shell confirm 1
debug3: send packet: type 98
debug2: channel_input_open_confirmation: channel 0: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Welcome to Ubuntu 16.04.4 LTS (GNU/Linux 4.4.0-116-generic x86_64)
所以区别是：
debug1: SSH2_MSG_KEXINIT sent <<-- this is where it stops
debug3: receive packet: type 20 <<-- this packet is never received when broken
debug1: SSH2_MSG_KEXINIT received