JAVA实现连接CentOS虚拟机的Telnet-Server

准备工程依赖包

依赖包：commons-net-2.0.jar
下载地址：https://repo1.maven.org/maven2/commons-net/commons-net/2.0/
选择commans-net-2.0.jar下载

Telnet server在CentOS，通过安装实现。

初始化JAVA项目

IDEA新建JAVA项目
在src目录新建NetTelnet类文件
项目下新建libs文件夹存放.jar文件
将commans-net-2.0.jar文件移动到libs目录
ctrl + shift + alt + s 添加依赖包

NetTelnet.java代码

/**  * commons-net-2.0.jar是工程依赖包   */

import org.apache.commons.net.telnet.TelnetClient;
import java.io.InputStream;
import java.io.PrintStream;
import java.util.Scanner;

public class NetTelnet {
    private TelnetClient telnet = new TelnetClient();
    private InputStream in;
    private PrintStream out;
    private char prompt = '$';

    /** 构造函数：初始化Telnet */
    public NetTelnet(String ip, int port, String user, String password) {
        try {
            telnet.connect(ip, port);
            in = telnet.getInputStream();
            out = new PrintStream(telnet.getOutputStream());
            // 根据root用户设置结束符
            this.prompt = user.equals("root") ? '#' : '$';
            login(user, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /** * 登录 * * @param user * @param password */
    public void login(String user, String password) {
        readUntil("login:");
        write(user);
        readUntil("Password:");
        write(password);
        readUntil(prompt + " ");
    }

    /** * 读取分析结果 * * @param pattern * @return */
    public String readUntil(String pattern) {
        try {
            char lastChar = pattern.charAt(pattern.length() - 1);
            StringBuffer sb = new StringBuffer();
            char ch = (char) in.read();
            while (true) {
                sb.append(ch);
                if (ch == lastChar) {
                    if (sb.toString().endsWith(pattern)) {
                        return sb.toString();
                    }
                }
                ch = (char) in.read();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /** * 写操作 * * @param value */
    public void write(String value) {
        try {
            out.println(value);
            out.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /** * 向目标发送命令字符串 * * @param command * @return */
    public String sendCommand(String command) {
        try {
            write(command);
            return readUntil(prompt + " ");
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /** * 关闭连接 */
    public void disconnect() {
        try {
            telnet.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        try {
            System.out.println("启动Telnet...");
            String ip = "172.16.1.190";
            int port = 23;
            String user = "calos";
            String password = "yegetaier570";
            NetTelnet telnet = new NetTelnet(ip, port, user, password);

            Scanner s = new Scanner(System.in);
            String input = s.nextLine();
            while (!input.equals("quit")){
                String r = telnet.sendCommand(input);
                System.out.println(r);

                input = s.nextLine();
            }

            telnet.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

run项目

IDEA运行测试项目
······
输入 quit 结束telnet连接