Ssh
如何調試：ssh_exchange_identification：連接被遠端主機關閉
通過私有 IP 進行 SSH 很好
我可以通過 SSH 通過其私有 IP 地址連接到伺服器：
C:\Users\m3>ssh -vvvvA uconn@192.168.1.11 OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5 debug3: Failed to open file:C:/Users/m3/.ssh/config error:2 debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2 debug2: resolve_canonicalize: hostname 192.168.1.11 is address debug2: ssh_connect_direct: needpriv 0 debug1: Connecting to 192.168.1.11 [192.168.1.11] port 22. debug1: Connection established. debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_rsa type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_rsa-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_dsa type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_dsa-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519 error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ed25519 type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ed25519-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_xmss type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_xmss-cert type -1 debug1: Local version string SSH-2.0-OpenSSH_for_Windows_7.7 debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.10 debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.10 pat OpenSSH* compat 0x04000000 debug2: fd 3 setting O_NONBLOCK debug1: Authenticating to 192.168.1.11:22 as 'uconn' debug3: hostkeys_foreach: reading file "C:\\Users\\m3/.ssh/known_hosts" debug3: record_hostkey: found key type ECDSA in file C:\\Users\\m3/.ssh/known_hosts:1 debug3: load_hostkeys: loaded 1 keys from 192.168.1.11 debug3: Failed to open file:C:/Users/m3/.ssh/known_hosts2 error:2 debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts error:2 debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts2 error:2 debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,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,curve25519-sha256@libssh.org,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: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1 debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1 debug2: compression ctos: none debug2: compression stoc: none debug2: languages ctos: debug2: languages stoc: debug2: first_kex_follows 0 debug2: reserved 0 debug2: peer server KEXINIT proposal debug2: KEX algorithms: curve25519-sha256@libssh.org,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: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1 debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1 debug2: compression ctos: none,zlib@openssh.com debug2: compression stoc: none,zlib@openssh.com debug2: languages ctos: debug2: languages stoc: debug2: first_kex_follows 0 debug2: reserved 0 debug1: kex: algorithm: curve25519-sha256@libssh.org debug1: kex: host key algorithm: ecdsa-sha2-nistp256 debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none debug1: kex: client->server cipher: chacha20-poly1305@openssh.com 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:eyPiBvKLgJOk1xJc0k6cx9UnwIXbUUaXu9pPHTKt5Rg debug3: hostkeys_foreach: reading file "C:\\Users\\m3/.ssh/known_hosts" debug3: record_hostkey: found key type ECDSA in file C:\\Users\\m3/.ssh/known_hosts:1 debug3: load_hostkeys: loaded 1 keys from 192.168.1.11 debug3: Failed to open file:C:/Users/m3/.ssh/known_hosts2 error:2 debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts error:2 debug3: Failed to open file:C:/ProgramData/ssh/ssh_known_hosts2 error:2 debug1: Host '192.168.1.11' is known and matches the ECDSA host key. debug1: Found key in C:\\Users\\m3/.ssh/known_hosts:1 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 debug3: unable to connect to pipe \\\\.\\pipe\\openssh-ssh-agent, error: 2 debug1: pubkey_prepare: ssh_get_authentication_socket: No such file or directory debug2: key: C:\\Users\\m3/.ssh/id_rsa (0000000000000000) debug2: key: C:\\Users\\m3/.ssh/id_dsa (0000000000000000) debug2: key: C:\\Users\\m3/.ssh/id_ecdsa (0000000000000000) debug2: key: C:\\Users\\m3/.ssh/id_ed25519 (0000000000000000) debug2: key: C:\\Users\\m3/.ssh/id_xmss (0000000000000000) 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: Trying private key: C:\\Users\\m3/.ssh/id_rsa debug3: no such identity: C:\\Users\\m3/.ssh/id_rsa: No such file or directory debug1: Trying private key: C:\\Users\\m3/.ssh/id_dsa debug3: no such identity: C:\\Users\\m3/.ssh/id_dsa: No such file or directory debug1: Trying private key: C:\\Users\\m3/.ssh/id_ecdsa debug3: no such identity: C:\\Users\\m3/.ssh/id_ecdsa: No such file or directory debug1: Trying private key: C:\\Users\\m3/.ssh/id_ed25519 debug3: no such identity: C:\\Users\\m3/.ssh/id_ed25519: No such file or directory debug1: Trying private key: C:\\Users\\m3/.ssh/id_xmss debug3: no such identity: C:\\Users\\m3/.ssh/id_xmss: No such file or directory debug2: we did not send a packet, disable method debug3: authmethod_lookup password debug3: remaining preferred: ,password debug3: authmethod_is_enabled password debug1: Next authentication method: password debug3: failed to open file:C:/dev/tty error:3 debug1: read_passphrase: can't open /dev/tty: No such file or directory uconn@192.168.1.11's password: debug3: send packet: type 50 debug2: we sent a password packet, wait for reply debug3: receive packet: type 52 debug1: Authentication succeeded (password). Authenticated to 192.168.1.11 ([192.168.1.11]: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 no-more-sessions@openssh.com debug3: send packet: type 80 debug1: Entering interactive session. debug1: pledge: network debug1: console supports the ansi parsing debug3: Successfully set console output code page from:437 to 65001 debug3: Successfully set console input code page from:437 to 65001 debug3: receive packet: type 80 debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0 debug3: receive packet: type 91 debug2: channel_input_open_confirmation: channel 0: callback start debug3: unable to connect to pipe \\\\.\\pipe\\openssh-ssh-agent, error: 2 debug1: ssh_get_authentication_socket: No such file or directory debug2: fd 3 setting TCP_NODELAY debug2: client_session2_setup: id 0 debug2: channel 0: request pty-req confirm 1 debug3: send packet: type 98 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 16.04.7 LTS (GNU/Linux 4.4.0-206-generic i686) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage 0 packages can be updated. 0 of these updates are security updates. New release '18.04.5 LTS' available. Run 'do-release-upgrade' to upgrade to it. Last login: Tue Mar 23 14:22:05 2021 from 192.168.1.52公共 IP 的 SSH 不好
但是，當使用它的公共 IP 地址時，我遇到了一個錯誤：
ssh_exchange_identification：連接被遠端主機關閉
C:\Users\m3>ssh -vvvvA uconn@11.111.11.111 OpenSSH_for_Windows_7.7p1, LibreSSL 2.6.5 debug3: Failed to open file:C:/Users/m3/.ssh/config error:2 debug3: Failed to open file:C:/ProgramData/ssh/ssh_config error:2 debug2: resolve_canonicalize: hostname 11.111.11.111 is address debug2: ssh_connect_direct: needpriv 0 debug1: Connecting to 11.111.11.111 [11.111.11.111] port 22. debug1: Connection established. debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_rsa type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_rsa-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_rsa-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_dsa type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_dsa-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_dsa-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ecdsa-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ecdsa-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519 error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ed25519 type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_ed25519-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_ed25519-cert type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_xmss type -1 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert error:2 debug3: Failed to open file:C:/Users/m3/.ssh/id_xmss-cert.pub error:2 debug1: key_load_public: No such file or directory debug1: identity file C:\\Users\\m3/.ssh/id_xmss-cert type -1 debug1: Local version string SSH-2.0-OpenSSH_for_Windows_7.7 ssh_exchange_identification: Connection closed by remote host如何調試
可能是什麼原因？如何調試問題？
路由器埠轉發
伺服器具有私有 IP 地址。但是有一個具有公共 IP 地址的路由器，它將 SSH 22 埠轉發到私有 IP 地址。
sshd日誌建議在這裡，我在伺服器上使用了這個命令來記錄
sshd輸出：$ tail -f -n 500 /var/log/auth.log | grep 'sshd'當我
ssh uconn@192.168.1.11在客戶端上執行時，我得到以下日誌：Mar 23 17:26:10 server-homeshine sshd[1355]: Accepted password for uconn from 192.168.1.52 port 53107 ssh2 Mar 23 17:26:10 server-homeshine sshd[1355]: pam_unix(sshd:session): session opened for user uconn by (uid=0)但是當我
ssh uconn@11.111.11.111在client上執行時，不會顯示任何日誌。我認為這暗示路由器在使用公共 IP 地址時不會轉發埠。22不知道為什麼。SSHD 配置
sshd伺服器上的配置是：uconn@server-homeshine:/etc/ssh$ cat sshd_config # Package generated configuration file # See the sshd_config(5) manpage for details # What ports, IPs and protocols we listen for Port 22 # Use these options to restrict which interfaces/protocols sshd will bind to ListenAddress :: ListenAddress 0.0.0.0 Protocol 2 # 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 #Privilege Separation is turned on for security UsePrivilegeSeparation yes # Lifetime and size of ephemeral version 1 server key KeyRegenerationInterval 3600 ServerKeyBits 1024 # Logging SyslogFacility AUTH LogLevel INFO # Authentication: LoginGraceTime 120 PermitRootLogin prohibit-password StrictModes yes RSAAuthentication yes PubkeyAuthentication yes #AuthorizedKeysFile %h/.ssh/authorized_keys # Don't read the user's ~/.rhosts and ~/.shosts files IgnoreRhosts yes # For this to work you will also need host keys in /etc/ssh_known_hosts RhostsRSAAuthentication no # similar for protocol version 2 HostbasedAuthentication no # Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication #IgnoreUserKnownHosts yes # To enable empty passwords, change to yes (NOT RECOMMENDED) PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with # some PAM modules and threads) ChallengeResponseAuthentication no # Change to no to disable tunnelled clear text passwords #PasswordAuthentication yes # Kerberos options #KerberosAuthentication no #KerberosGetAFSToken no #KerberosOrLocalPasswd yes #KerberosTicketCleanup yes # GSSAPI options #GSSAPIAuthentication no #GSSAPICleanupCredentials yes X11Forwarding yes X11DisplayOffset 10 PrintMotd no PrintLastLog yes TCPKeepAlive yes #UseLogin no #MaxStartups 10:30:60 #Banner /etc/issue.net # Allow client to pass locale environment variables AcceptEnv LANG LC_* Subsystem sftp /usr/lib/openssh/sftp-server # 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 yesIP 表
這是伺服器上的 IP 表：
$ sudo iptables -S -P INPUT ACCEPT -P FORWARD ACCEPT -P OUTPUT ACCEPT$ sudo ip6tables -S -P INPUT ACCEPT -P FORWARD ACCEPT -P OUTPUT ACCEPT路由表
伺服器路由表：
$ sudo route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 enp9s0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 enp9s0Wireshark/Tshark
tshark在伺服器上安裝並檢查網路數據包，表明在客戶端ssh uconn@192.168.1.11上執行（私有 IP）時，SSH 數據包被伺服器接收。但是在客戶端
ssh uconn@11.111.11.111上執行（公共 IP）時，伺服器不會收到任何 SSH 數據包。結論是 ADSL 路由器沒有將 SSH 數據包轉發到伺服器。
合勤詢價
就這個問題聯繫了合勤，收到了這樣的回复：
在進行埠轉發時，您需要確保內部伺服器具有指向網關的網關地址，以便能夠響應外部請求。
還要檢查網關本身是否未使用埠 22。
伺服器預設網關
我的伺服器預設網關是
192.168.1.1它應該是什麼：$ ip r default via 192.168.1.1 dev enp9s0 onlink 192.168.1.0/24 dev enp9s0 proto kernel scope link src 192.168.1.11
出於安全原因，ISP 關閉了埠 22 傳入。通過聯繫 ISP 想通了。
將 SSHD 埠從更改
22為2222：$ sudo vim /etc/ssh/sshd_config $ sudo systemctl restart sshd現在我可以使用自定義埠通過 SSH 連接到公共 IP 地址：
>ssh uconn@11.111.11.111 -p 2222