java简单实现telnet协议（关键在于需解析telnet协议里的选项协商）

import java.io.BufferedInputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.Socket;import java.net.UnknownHostException;public class Telnet {Socket serverSocket; // 连接用socketpublic OutputStream serverOutput; // 用于网络输出的流public BufferedInputStream serverInput; // 用于网络输入的流String host; // 连接服务器的地址int port; // 连接服务器的端口号static final int DEFAULT_TELNET_PORT = 23; // telnet的端口号(23号)// 构造器(1):指定地址和端口号时用public Telnet(String host, int port) {this.host = host;this.port = port;}// 构造器(2)只指定地址时用public Telnet(String host) {this(host, DEFAULT_TELNET_PORT); // 假定为Telnet端口}// openConnection 方法// 由地址和端口号虽构成Socket而开成流public void openConnection() throws IOException, UnknownHostException {serverSocket = new Socket(host, port);serverOutput = serverSocket.getOutputStream();serverInput = new BufferedInputStream(serverSocket.getInputStream());// 若连接的是Telnet端口则进行协商if (port == DEFAULT_TELNET_PORT) {negotiation(serverInput, serverOutput);}}// main_proc方法// 启动进行网络处理的线程public void main_proc() throws IOException {try {// 生成线程用streamConnector类的对象StreamConnector stdin_to_socket = new StreamConnector(System.in,serverOutput);StreamConnector socket_to_stdout = new StreamConnector(serverInput,System.out);// 生成线程Thread input_thread = new Thread(stdin_to_socket);Thread output_thread = new Thread(socket_to_stdout);// 启动线程input_thread.start();output_thread.start();} catch (Exception e) {System.err.print(e);System.exit(1);}}// 定义用于协商的命令static final byte IAC = (byte) 255;static final byte DONT = (byte) 254;static final byte DO = (byte) 253;static final byte WONT = (byte) 252;static final byte WILL = (byte) 251;// negotiation 方法// 利用NVT进行协商通信static void negotiation(BufferedInputStream in, OutputStream out)throws IOException {byte[] buff = new byte[3]; // 接收命令的数组while (true) {in.mark(buff.length);if (in.available() >= buff.length) {in.read(buff);if (buff[0] != IAC) { // 协商结束in.reset();return;} else if (buff[1] == DO) { // 对于DO命令......buff[1] = WONT; // 用WONT作为应答out.write(buff);}}}}// main方法// 建立TCP连接,开始处理public static void main(String[] arg) {try {Telnet t = null;// 由参数个数决定调用哪个构造器// switch (arg.length) {// case 1: //只指定服务器地址// t = new Telnet(arg[0]);// break;// case 2: //指定地址和端口// t = new Telnet(arg[0], Integer.parseInt(arg[1]));// break;// default: //使用方法不正确时// System.out.println(// "usage:java Telnet <host name> { <port number> } ");// return;// }t = new Telnet("222.211.88.185", 23);t.openConnection();t.main_proc();} catch (Exception e) {e.printStackTrace();System.exit(1);}}}// StreamConnector类// 接收流参数以二者结合实现数据传递// StreamConnector类是用于构造线程序的类class StreamConnector implements Runnable {InputStream src = null;OutputStream dist = null;// 构造器 接收输入输出流public StreamConnector(InputStream in, OutputStream out) {src = in;dist = out;}// 执行处理的函数体// 无限循环进行流的读写public void run() {byte[] buff = new byte[1024];while (true) {try {int n = src.read(buff);if (n > 0) {dist.write(buff, 0, n);}} catch (Exception e) {e.printStackTrace();System.err.print(e);System.exit(1);}}}}