我無法透過 SSH 連接到我的伺服器，我不知道原因。
SSHD 其運作和連接埠在 UFW 中開放。我嘗試更改端口，但問題仍然存在。也嘗試了不同的機器和網路。
如果我重新啟動伺服器，有時可以建立連接，但一段時間後問題又出現。
我的 sshd_config：
# $OpenBSD: sshd_config,v 1.103 2018/04/09 20:41:22 tj Exp $
# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options override the
# default value.
Port 1402
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key
# Ciphers and keying
#RekeyLimit default none
# Logging
#SyslogFacility AUTH
LogLevel VERBOSE
# Authentication:
#LoginGraceTime 2m
#PermitRootLogin prohibit-password
StrictModes yes
#MaxAuthTries 6
#MaxSessions 10
#PubkeyAuthentication yes
# Expect .ssh/authorized_keys2 to be disregarded by default in future.
#AuthorizedKeysFile .ssh/authorized_keys .ssh/authorized_keys2
#AuthorizedPrincipalsFile none
#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes
# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
PermitEmptyPasswords no
# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication yes
# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication. Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes
#AllowAgentForwarding yes
AllowTcpForwarding no
#GatewayPorts no
X11Forwarding no
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#PermitUserEnvironment no
#Compression delayed
KeepAlive yes
ClientAliveInterval 90000
ClientAliveCountMax 2
UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none
# no default banner path
#Banner none
# Allow client to pass locale environment variables
AcceptEnv LANG LC_*
# override default of no subsystems
Subsystem sftp /usr/lib/openssh/sftp-server
# Example of overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding no
# PermitTTY no
# ForceCommand cvs server
PermitRootLogin no
PasswordAuthentication yes
我收到超時錯誤：ssh[電子郵件受保護]-p 1402
nmap 回答以下問題：
user@linux:~$ nmap -p 1402 -Pn xx.xxx.xxx.xxx
Starting Nmap 7.70 ( https://nmap.org ) at 2021-09-07 22:06 CEST
Nmap scan report for xx.xxx.xxx.xxx
Host is up.
PORT STATE SERVICE
1402/tcp filtered prm-sm-np
Nmap done: 1 IP address (1 host up) scanned in 6.99 seconds
一些想法？
編輯
UFW配置
user@localhost:~$ sudo ufw status verbose
[sudo] password for user:
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip
To Action From
-- ------ ----
1402/tcp LIMIT IN Anywhere
3000/tcp ALLOW IN Anywhere
9100/tcp ALLOW IN Anywhere
12798/tcp ALLOW IN Anywhere
6000/tcp ALLOW IN Anywhere
60000/tcp ALLOW IN Anywhere
1402/tcp (v6) LIMIT IN Anywhere (v6)
3000/tcp (v6) ALLOW IN Anywhere (v6)
9100/tcp (v6) ALLOW IN Anywhere (v6)
12798/tcp (v6) ALLOW IN Anywhere (v6)
6000/tcp (v6) ALLOW IN Anywhere (v6)
60000/tcp (v6) ALLOW IN Anywhere (v6)
答案1
KeepAlive yes
ClientAliveInterval 90000
ClientAliveCountMax 2
這三行表示如果在90000*2秒內沒有客戶端發來TCP包，就會自動斷開連線。
這是SSH的一種保護機制。您可以變更參數或使用 Bitvise ssh 用戶端，這會自動將 TCP Ping-Pong 心跳包傳送到伺服器。