Java使用Socket发送字符串给FTP服务器端

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import java.io.InputStream;??
import java.io.OutputStream;??
import java.net.Socket;??public class FTPClient{
??? public static void main(String[] args) throws Exception{??
??????? Socket socket = new Socket("192.168.0.1",21);??
??????? InputStream is = socket.getInputStream();??
??????? OutputStream os = socket.getOutputStream();??????? //接收初始链接信息
??????? byte[] buffer = new byte[100];
??????? int length = is.read(buffer);
??????? String s = new String(buffer, 0, length);
??????? System.out.println(s);
??????? //发送用户名
??????? String str = "USER useway/n";
??????? os.write(str.getBytes());
??????? //得到返回值
??????? length = is.read(buffer);
??????? s = new String(buffer, 0, length);
??????? System.out.println(s);???????
??????? //发送密码
??????? str = "PASS !@#$%abcd/n";
??????? os.write(str.getBytes());
//得到返回值
??????? length = is.read(buffer);
??????? s = new String(buffer, 0, length);
??????? System.out.println(s);
??????? //发送切换文件夹指令
??????? str = "CWD /home/useway/n";
??????? os.write(str.getBytes());
??????? //得到返回值
??????? length = is.read(buffer);
??????? s = new String(buffer, 0, length);
??????? System.out.println(s);
??????? //设置模式
??????? str = "EPSV ALL/n";
??????? os.write(str.getBytes());
??????? //得到返回值
??????? length = is.read(buffer);
??????? s = new String(buffer, 0, length);
??????? System.out.println(s);???????
??????? //得到被动监听信息
??????? str = "EPSV/n";
??????? os.write(str.getBytes());
??????? //得到返回值
??????? length = is.read(buffer);
??????? s = new String(buffer, 0, length);
??????? System.out.println(s);
??????? //取得FTP被动监听的端口号
??????? String portlist=s.substring(s.indexOf("(|||")+4,s.indexOf("|)"));
??????? System.out.println(portlist);
??????? //实例化ShowList线程类，链接FTP被动监听端口号
??????? ShowList sl=new ShowList();
??????? sl.port=Integer.parseInt(portlist);
??????? sl.start();
??????? //执行LIST命令
??????? str = "LIST/n";
??????? os.write(str.getBytes());
??????? //得到返回值
??????? length = is.read(buffer);
??????? s = new String(buffer, 0, length);
??????? System.out.println(s);
??????? //关闭链接
??????? is.close();
??????? os.close();
??????? socket.close();
??? }
}
//得到被动链接信息类，这个类是多线程的
class ShowList extends Thread{
?public int port=0;
??? public void run(){
??? ?try{
???????? Socket socket = new Socket("192.168.0.1",this.port);
???????? InputStream is = socket.getInputStream();
???????? OutputStream os = socket.getOutputStream();
???????? byte[] buffer = new byte[10000];
???????? int length = is.read(buffer);
???????? String s = new String(buffer, 0, length);
???????? System.out.println(s);
??????????? //关闭链接
??????????? is.close();
??????????? os.close();
??????????? socket.close();
??? ?}
??? ?catch(Exception ex){
??? ?}
??? }
}

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