我整个下午都被这个问题困扰了，不知道怎么回事。我之所以需要使用 sftp 命令是因为我在 shell 脚本中使用它。如果我可以使用 CentOS 7 附带的另一个程序，允许我使用 SFTP 下载文件，那么请赐教。
编辑1
使用的 SFTP 客户端：WinSCP 和 PSFTP。
在同一网络和互联网上运行的不同计算机上对此进行了测试（此处仅使用 IP 地址）。这在同一台计算机上按预期工作（使用本地主机和环回地址）。
Firewalld 服务已停止，并且任何时候都没有使用或配置任何代理。
我收到的错误是（使用 sftp -vvv sftp@hostname）：
debug1: connect to ipaddress port 22: Connection timed out
ssh: connect to host ipaddress port 22: Connection timed out
Couldn't read packet: Connection reset by peer
我的 sshd_config 文件（服务器端）：
# $OpenBSD: sshd_config,v 1.93 2014/01/10 05:59:19 djm Exp $
# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/local/bin:/usr/bin
# 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.
# If you want to change the port on a SELinux system, you have to tell
# SELinux about this change.
# semanage port -a -t ssh_port_t -p tcp #PORTNUMBER
#
#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
# The default requires explicit activation of protocol 1
#Protocol 2
# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 1024
# Ciphers and keying
#RekeyLimit default none
# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
SyslogFacility AUTHPRIV
#LogLevel INFO
# Authentication:
#LoginGraceTime 2m
PermitRootLogin yes
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10
#RSAAuthentication yes
#PubkeyAuthentication yes
# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
# but this is overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile .ssh/authorized_keys
#AuthorizedPrincipalsFile none
#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and 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
PasswordAuthentication yes
# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no
# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
#KerberosUseKuserok yes
# GSSAPI options
#GSSAPIAuthentication yes
GSSAPIAuthentication no
GSSAPICleanupCredentials no
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
#GSSAPIEnablek5users 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'.
# WARNING: 'UsePAM no' is not supported in Red Hat Enterprise Linux and may cause several
# problems.
UsePAM yes
#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
UsePrivilegeSeparation sandbox # Default for new installations.
#PermitUserEnvironment no
#Compression delayed
ClientAliveInterval 60
#ClientAliveCountMax 3
#ShowPatchLevel no
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none
# no default banner path
#Banner none
# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS
# override default of no subsystems
Subsystem sftp internal-sftp
# Example of overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding no
# PermitTTY no
# ForceCommand cvs server
Match User sftp
ForceCommand internal-sftp
PasswordAuthentication yes
ChrootDirectory /home/sftp
PermitTunnel no
AllowAgentForwarding no
AllowTcpForwarding no
X11Forwarding no
用于创建用户的代码：
mkdir -p /home/sftp
chown root /home/sftp
chmod 755 -R /home/sftp
useradd -d /home/sftp -r sftp
usermod -s /sbin/nologin sftp
echo "password" | passwd --stdin sftp
我还没有接触过客户端的 sshd_config 文件，所以我猜这只是安装时的默认值（在我的实现中，我无法更改这些配置文件）。
答案1
您的 WinSCP 是否配置为使用任何类型的代理？仅当您使用 PuTTY 配置对话框保存会话配置（包括代理设置）然后使用 .PSFTP 时，PSFTP 才能使用代理psftp -load <name of saved session>。
或者您的一个 SFTP 客户端是否可能尝试使用 IPv4 和另一个 IPv6，但只允许其中之一？ （即，如果您在 WinSCP 中使用主机名，它可能会查找 IPv6 和 IPv4 地址并使用 IPv6 地址。）