Telnet 命令进入（通过，内部）SSH 会话

Question

我有一个任务：通过 ssh 会话执行 telnet 命令。

我读过类似的问题：

1. 使用 JSch 在远程 SSH 会话上运行 telnet 命令
2. 通过 SSH 远程登录
3. 使用 JSch 在远程 SSH 会话上运行 telnet 命令后执行挂起

我写了代码（使用 lib https://mvnrepository.com/artifact/com.jcraft/jsch ）：

1. 类 Ssh：

   公共类 Ssh { 私有最终字符串用户； 私人最终字符串密码； 私人最终字符串主机；

    public Ssh(String user, String password, String host) { this.USER = user; this.PASSWORD = password; this.HOST = host; } public Session runSsh() { try { Session session = new JSch().getSession(USER, HOST, 22); session.setPassword(PASSWORD); // It must not be recommended, but if you want to skip host-key check, session.setConfig("StrictHostKeyChecking", "no"); session.connect(3000); return session; } catch (JSchException e) { System.out.println(e); } return null; }

   }

2. 类 Telnet

   公共类 Telnet {

    public String runCommand(Session session, String command) throws Exception { Channel channel = session.openChannel("shell"); channel.connect(3000); DataOutputStream outputStream = new DataOutputStream(channel.getOutputStream()); outputStream.writeBytes("telnet localhost 5000\\r\\n"); outputStream.writeBytes(command + "\\r\\n"); outputStream.writeBytes("exit\\r\\n"); outputStream.flush(); DataInputStream inputStream = new DataInputStream(channel.getInputStream()); BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)); channel.setInputStream(inputStream, true); String line = reader.readLine(); String result = line +"\\n"; while (!(line= reader.readLine()).equals("exit")){ result += line +"\\n"; } result += "Connection closed by foreign host"; outputStream.close(); inputStream.close(); channel.disconnect(); session.disconnect(); return result; }

   }

3. 班级主要

   公共课主要{

    public static void main(String[] arg) { Ssh ssh = new Ssh("user","password","ip-server"); Telnet telnet = new Telnet(); try { Session sessionSsh = ssh.runSsh(); String result = telnet.runCommand(sessionSsh, "H"); System.out.println(result); } catch (Exception e) { e.printStackTrace(); } }

   }

我得到结果：

telnet localhost 5000


Entering character mode

Escape character is '^]'.




 Command Shell 1 on intelpc-1 (Port: 5000)

 b01_1_1 (5000) >
H

Connection closed by foreign host

Process finished with exit code 0

我没有看到执行命令 telnet 的结果...

我通过 telnet 做了不同的命令：

- H
or
- u s3

但我看不到他们的结果:(

请告诉我。 如何获取telnet命令执行的结果？

Answer 1

我调试了您的示例，就我而言，我需要等待您通过 telnet 连接的程序，直到它准备好接收命令。

在第二步中，您可以发送您的命令和退出命令来停止 telnet，因此您正在从流中读取数据，直到它通过说“连接关闭...”而停止。 请注意，从 telnet 退出可以有不同的命令，有些使用quit ，有些使用exit或只等待终止信号。

 class Telnet {

        public String runCommand(Session session, String command) throws Exception {
            Channel channel = session.openChannel("shell");
            channel.connect(3000);

            DataOutputStream outputStream = new DataOutputStream(channel.getOutputStream());

            outputStream.writeBytes("telnet localhost 16379\r\n");
            outputStream.flush();

            DataInputStream inputStream = new DataInputStream(channel.getInputStream());
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

            channel.setInputStream(inputStream, true);

            // Read until we are ready to write
            String line;
            while (!(line= reader.readLine()).equals("Escape character is '^]'.")){
                System.out.println(line);
            }

            // write command and exit telnet
            outputStream.writeBytes(command + "\r\n");
            outputStream.writeBytes("quit\r\n");
            outputStream.flush();

            // read until telnet has closed
            String result = "";
            while (!(line= reader.readLine()).equals("Connection closed by foreign host.")){
                result += line +"\n";
            }

            outputStream.close();
            inputStream.close();
            channel.disconnect();
            session.disconnect();

            return result;
        }
    }

最后，还有其他无需 telnet 的通信方式，即本地端口转发。

Answer 2

感谢马蒂亚斯·维德曼。

我按照 Matthias Wiedemann 的建议使用了 SSH 隧道https://www.ssh.com/academy/ssh/tunneling/example 。

全部的：

1 步。 通过 SSH 连接并创建会话 SSH

SSH ssh = new SSH(user, password, host, port);
Session session = SSHUtil.createSession(ssh);

2 步。 使用 SSH 创建隧道

SSHUtil.createChannel(session, outputConsole);
SSHUtil.createSshTunnel(session, port);

3 步。 通过 Telnet 连接并使用隧道端口执行 Telnet 命令（端口变为 9999，而不是 5000）。

clientForTelnet = new ClientForTelnet(new Telnet(host, port));
outputConsole.print(TelnetUtil.connect(clientForTelnet));

outputConsole 是 PrintStream。

我得到以下信息：

1.

public class SSHUtil{

    private final static Logger LOGGER = LogManager.getLogger(SSHUtil.class);

    public static Session createSession(SSH ssh) {
        Session session = null;
        try {
            session = new JSch().getSession(ssh.getUSER(), ssh.getHOST().getIp(), ssh.getPORT().getPort());
            session.setPassword(ssh.getPASSWORD());
            session.setConfig("StrictHostKeyChecking", "no"); // It must not be recommended, but if you want to skip host-key check
            session.connect(10000);
            LOGGER.info("SSH session created");
        } catch (JSchException e) {
            LOGGER.error("SSH session not created " + e);
        }
        return session;
    }

    public static Channel createChannel(Session session, PrintStream output) {
        Channel channel = null;
        try {
            channel = session.openChannel("shell");
            channel.setInputStream(System.in);
            channel.setOutputStream(output);
            //  streamOut = channel.getOutputStream();

            channel.connect(10000);
            LOGGER.info("SSH channel created");
        } catch (JSchException e) {
            LOGGER.error("SSH channel not created " + e);
        }
        return channel;
    }

    public static void createSshTunnel(Session session, Port port) {
        // TODO сделать пул портов, чтобы исключить вероятность, что порт 9999 занят
        try {
            session.setPortForwardingL(9999, session.getHost(), port.getPort());
            LOGGER.info("Tunnel created localhost:" + 9999 + " -> " + session.getHost() + ":" + port.getPort());
        } catch (JSchException e) {
            LOGGER.error("SSH tunnel not created " + e);
        }
    }

    public static void disconnect(Session session) {
        if (session != null && session.isConnected()) {
            session.disconnect();
        }
    }

}

2. 公共类 TelnetUtil {

    private final static Logger LOGGER = LogManager.getLogger(TelnetUtil.class);

    public static String connect(ClientForTelnet clientForTelnet) {
        try {
            // Connect to the server
            clientForTelnet.getTc().connect(clientForTelnet.getTelnet().getHOST().getIp(), clientForTelnet.getTelnet().getPORT().getPort());

            // Get input and output stream references
            clientForTelnet.setIn(clientForTelnet.getTc().getInputStream());
            clientForTelnet.setOut(new PrintStream(clientForTelnet.getTc().getOutputStream()));
        } catch (IOException e) {
            LOGGER.error(e);
        }

        return readUntil(clientForTelnet.getPrompt(), clientForTelnet.getIn());
    }

    public static String readUntil(String pattern, InputStream in) {
        StringBuilder sb = new StringBuilder();
        try {
            char lastChar = pattern.charAt(pattern.length() - 1);
            boolean found = false;
            char ch = (char) in.read();
            while (true) {
           //     System.out.print(ch);
                sb.append(ch);
                if (ch == lastChar) {
                    if (sb.toString().endsWith(pattern)) {
                        return sb.toString();
                    }
                }
                ch = (char) in.read();
            }
        } catch (IOException e) {
            LOGGER.error(e);
        }
        return sb.toString();
    }

    public static void write(String value, PrintStream out) {
        out.println(value);
        out.flush();
    }

    public static String sendCommand(ClientForTelnet clientForTelnet, String command) {
        write(command, clientForTelnet.getOut());
        return readUntil(clientForTelnet.getPrompt(), clientForTelnet.getIn());
    }

    public static void disconnect(TelnetClient tc) {
        try {
            tc.disconnect();
        } catch (IOException e) {
            LOGGER.error(e);
        }
    }

}

3. 公共类 SSH { 私有最终字符串用户； 私人最终字符串密码； 私人最终主机 HOST； 私有最终端口 PORT；

    private final Port DEFAULT_PORT = new Port(22); public SSH(String user, String password, Host host, Port port) { this.USER = user; this.PASSWORD = password; this.HOST = host; this.PORT = port; } public SSH(String user, String password, Host host) { this.USER = user; this.PASSWORD = password; this.HOST = host; this.PORT = DEFAULT_PORT; } public String getUSER() { return USER; } public String getPASSWORD() { return PASSWORD; } public Host getHOST() { return HOST; } public Port getPORT() { return PORT; }

   }

4. 公共类 Telnet {

    private final Host HOST; private final Port PORT; private final Port DEFAULT_PORT = new Port(5000); public Telnet(Host host, Port port) { this.HOST = host; this.PORT = port; } public Telnet(Host host) { this.HOST = host; this.PORT = DEFAULT_PORT; } public Host getHOST() { return HOST; } public Port getPORT() { return PORT; }

   }

5. 公共类 ClientForTelnet {

    private final TelnetClient TC = new TelnetClient(); private final String PROMT = ">"; private final Telnet TELNET; private InputStream in; private PrintStream out; public ClientForTelnet(Telnet telnet) { this.TELNET = telnet; } public InputStream getIn() { return in; } public PrintStream getOut() { return out; } public Telnet getTelnet() { return TELNET; } public String getPrompt() { return PROMT; } public TelnetClient getTc() { return TC; } public void setIn(InputStream in) { this.in = in; } public void setOut(PrintStream out) { this.out = out; }

   }

public class Host {

    private final static Logger LOGGER = LogManager.getLogger(Host.class);

    private String ip;

    public Host(String ip) {
        this.ip = ip;
    }

    public String getIp() {
        return ip;
    }

}