FTP(File Transfer Protocol 文件传输协议)是Internet 上用来传送文件的协议。在Internet上通过FTP 服务器可以进行文件的上传(Upload)或下载(Download)。FTP是实时联机服务，在使用它之前必须是具有该服务的一个用户(用户名和口令)，工作时客户端必须先登录到作为服务器一方的计算机上，用户登录后可以进行文件搜索和文件传送等有关操作，如改变当前工作目录、列文件目录、设置传输参数及传送文件等。使用FTP可以传送所有类型的文件，如文本文件、二进制可执行文件、图象文件、声音文件和数据压缩文件等。
FTP 命令
FTP 的主要操作都是基于各种命令基础之上的。常用的命令有：
设置传输模式，它包括ASCⅡ(文本) 和BINARY 二进制模式;
目录操作，改变或显示远程计算机的当前目录(cd、dir/ls 命令);
连接操作，open命令用于建立同远程计算机的连接；close命令用于关闭连接;
发送操作，put命令用于传送文件到远程计算机；mput 命令用于传送多个文件到远程计算机;
获取操作，get命令用于接收一个文件；mget命令用于接收多个文件。
import java.net.Socket; import org.apache.log4j.Logger; /** * 角色――服务器A * @author Leon * */ public class ServerA{ public static void main(String[] args){ final String F_DIR = "c:/test";//根路径 final int PORT = 22;//监听端口号 Logger.getRootLogger(); Logger logger = Logger.getLogger("com"); try{ ServerSocket s = new ServerSocket(PORT); logger.info("Connecting to server A..."); logger.info("Connected Successful! Local Port:"+s.getLocalPort()+". Default Directory:'"+F_DIR+"'."); while( true ){ //接受客户端请求 Socket client = s.accept(); //创建服务线程 new ClientThread(client, F_DIR).start(); } } catch(Exception e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } } import java.io.BufferedReader; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.PrintWriter; import java.io.RandomAccessFile; import java.net.ConnectException; import java.net.InetAddress; import java.net.ServerSocket; import java.net.Socket; import java.net.UnknownHostException; import java.nio.charset.Charset; import java.util.Random; import org.apache.log4j.Logger; /** * 客户端子线程类 * @author Leon * */ public class ClientThread extends Thread { private Socket socketClient;//客户端socket private Logger logger;//日志对象 private String dir;//绝对路径 private String pdir = "/";//相对路径 private final static Random generator = new Random();//随机数 public ClientThread(Socket client, String F_DIR){ this.socketClient = client; this.dir = F_DIR; } @Override public void run() { Logger.getRootLogger(); logger = Logger.getLogger("com"); InputStream is = null; OutputStream os = null; try { is = socketClient.getInputStream(); os = socketClient.getOutputStream(); } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } BufferedReader br = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8"))); PrintWriter pw = new PrintWriter(os); String clientIp = socketClient.getInetAddress().toString().substring(1);//记录客户端IP String username = "not logged in";//用户名 String password = "";//口令 String command = "";//命令 boolean loginStuts = false;//登录状态 final String LOGIN_WARNING = "530 Please log in with USER and PASS first."; String str = "";//命令内容字符串 int port_high = 0; int port_low = 0; String retr_ip = "";//接收文件的IP地址 Socket tempsocket = null; //打印欢迎信息 pw.println("220-FTP Server A version 1.0 written by Leon Guo"); pw.flush(); logger.info("("+username+") ("+clientIp+")> Connected, sending welcome message..."); logger.info("("+username+") ("+clientIp+")> 220-FTP Server A version 1.0 written by Leon Guo"); boolean b = true; while ( b ){ try { //获取用户输入的命令 command = br.readLine(); if(null == command) break; } catch (IOException e) { pw.println("331 Failed to get command"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 331 Failed to get command"); logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } b = false; } /* * 访问控制命令 */ // USER命令 if(command.toUpperCase().startsWith("USER")){ logger.info("(not logged in) ("+clientIp+")> "+command); username = command.substring(4).trim(); if("".equals(username)){ pw.println("501 Syntax error"); pw.flush(); logger.info("(not logged in) ("+clientIp+")> 501 Syntax error"); username = "not logged in"; } else{ pw.println("331 Password required for " + username); pw.flush(); logger.info("(not logged in) ("+clientIp+")> 331 Password required for " + username); } loginStuts = false; } //end USER // PASS命令 else if(command.toUpperCase().startsWith("PASS")){ logger.info("(not logged in) ("+clientIp+")> "+command); password = command.substring(4).trim(); if(username.equals("root") && password.equals("root")){ pw.println("230 Logged on"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 230 Logged on"); // logger.info("客户端 "+clientIp+" 通过 "+username+"用户登录"); loginStuts = true; } else{ pw.println("530 Login or password incorrect!"); pw.flush(); logger.info("(not logged in) ("+clientIp+")> 530 Login or password incorrect!"); username = "not logged in"; } } //end PASS // PWD命令 else if(command.toUpperCase().startsWith("PWD")){ logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ // logger.info("用户"+clientIp+"："+username+"执行PWD命令"); pw.println("257 /""+pdir+"/" is current directory"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 257 /""+pdir+"/" is current directory"); } else{ pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end PWD // CWD命令 else if(command.toUpperCase().startsWith("CWD")){ logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ str = command.substring(3).trim(); if("".equals(str)){ pw.println("250 Broken client detected, missing argument to CWD. /""+pdir+"/" is current directory."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 250 Broken client detected, missing argument to CWD. /""+pdir+"/" is current directory."); } else{ //判断目录是否存在 String tmpDir = dir + "/" + str; File file = new File(tmpDir); if(file.exists()){//目录存在 dir = dir + "/" + str; if("/".equals(pdir)){ pdir = pdir + str; } else{ pdir = pdir + "/" + str; } // logger.info("用户"+clientIp+"："+username+"执行CWD命令"); pw.println("250 CWD successful. /""+pdir+"/" is current directory"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 250 CWD successful. /""+pdir+"/" is current directory"); } else{//目录不存在 pw.println("550 CWD failed. /""+pdir+"/": directory not found."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 550 CWD failed. /""+pdir+"/": directory not found."); } } } else{ pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end CWD // QUIT命令 else if(command.toUpperCase().startsWith("QUIT")){ logger.info("("+username+") ("+clientIp+")> "+command); b = false; pw.println("221 Goodbye"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 221 Goodbye"); try { Thread.currentThread(); Thread.sleep(1000); } catch (InterruptedException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } //end QUIT /* * 传输参数命令 */ //PORT命令，主动模式传输数据 else if(command.toUpperCase().startsWith("PORT")){ logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ try { str = command.substring(4).trim(); port_low = Integer.parseInt(str.substring(str.lastIndexOf(",")+1)); port_high = Integer.parseInt(str.substring(0, str.lastIndexOf(",")) .substring(str.substring(0, str.lastIndexOf(",")).lastIndexOf(",")+1)); String str1 = str.substring(0, str.substring(0, str.lastIndexOf(",")).lastIndexOf(",")); retr_ip = str1.replace(",", "."); try { //实例化主动模式下的socket tempsocket = new Socket(retr_ip,port_high * 256 + port_low); // logger.info("用户"+clientIp+"："+username+"执行PORT命令"); pw.println("200 port command successful"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 200 port command successful"); } catch (ConnectException ce) { pw.println("425 Can't open data connection."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 425 Can't open data connection."); logger.error(ce.getMessage()); for(StackTraceElement ste : ce.getStackTrace()){ logger.error(ste.toString()); } } catch (UnknownHostException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } catch (NumberFormatException e) { pw.println("503 Bad sequence of commands."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 503 Bad sequence of commands."); logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } else{ pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end PORT //PASV命令，被动模式传输数据 else if(command.toUpperCase().startsWith("PASV")) { logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ ServerSocket ss = null; while( true ){ //获取服务器空闲端口 port_high = 1 + generator.nextInt(20); port_low = 100 + generator.nextInt(1000); try { //服务器绑定端口 ss = new ServerSocket(port_high * 256 + port_low); break; } catch (IOException e) { continue; } } // logger.info("用户"+clientIp+"："+username+"执行PASV命令"); InetAddress i = null; try { i = InetAddress.getLocalHost(); } catch (UnknownHostException e1) { e1.printStackTrace(); } pw.println("227 Entering Passive Mode ("+i.getHostAddress().replace(".", ",")+","+port_high+","+port_low+")"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 227 Entering Passive Mode ("+i.getHostAddress().replace(".", ",")+","+port_high+","+port_low+")"); try { //被动模式下的socket tempsocket = ss.accept(); ss.close(); } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } else{ pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end PASV //RETR命令 else if(command.toUpperCase().startsWith("RETR")){ logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ str = command.substring(4).trim(); if("".equals(str)){ pw.println("501 Syntax error"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 501 Syntax error"); } else { try { pw.println("150 Opening data channel for file transfer."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 150 Opening data channel for file transfer."); RandomAccessFile outfile = null; OutputStream outsocket = null; try { //创建从中读取和向其中写入（可选）的随机访问文件流，该文件具有指定名称 outfile = new RandomAccessFile(dir+"/"+str,"r"); outsocket = tempsocket.getOutputStream(); } catch (FileNotFoundException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } byte bytebuffer[]= new byte[1024]; int length; try{ while((length = outfile.read(bytebuffer)) != -1){ outsocket.write(bytebuffer, 0, length); } outsocket.close(); outfile.close(); tempsocket.close(); } catch(IOException e){ logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } // logger.info("用户"+clientIp+"："+username+"执行RETR命令"); pw.println("226 Transfer OK"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 226 Transfer OK"); } catch (Exception e){ pw.println("503 Bad sequence of commands."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 503 Bad sequence of commands."); logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } } else{ pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } }//end RETR //STOR命令 else if(command.toUpperCase().startsWith("STOR")){ logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ str = command.substring(4).trim(); if("".equals(str)){ pw.println("501 Syntax error"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 501 Syntax error"); } else { try { pw.println("150 Opening data channel for file transfer."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 150 Opening data channel for file transfer."); RandomAccessFile infile = null; InputStream insocket = null; try { infile = new RandomAccessFile(dir+"/"+str,"rw"); insocket = tempsocket.getInputStream(); } catch (FileNotFoundException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } byte bytebuffer[] = new byte[1024]; int length; try{ while((length =insocket.read(bytebuffer) )!= -1){ infile.write(bytebuffer, 0, length); } insocket.close(); infile.close(); tempsocket.close(); } catch(IOException e){ logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } // logger.info("用户"+clientIp+"："+username+"执行STOR命令"); pw.println("226 Transfer OK"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 226 Transfer OK"); } catch (Exception e){ pw.println("503 Bad sequence of commands."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 503 Bad sequence of commands."); logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } } else { pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end STOR //NLST命令 else if(command.toUpperCase().startsWith("NLST")) { logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ try { pw.println("150 Opening data channel for directory list."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 150 Opening data channel for directory list."); PrintWriter pwr = null; try { pwr= new PrintWriter(tempsocket.getOutputStream(),true); } catch (IOException e1) { e1.printStackTrace(); } File file = new File(dir); String[] dirstructure = new String[10]; dirstructure= file.list(); for(int i=0;i<dirstructure.length;i++){ pwr.println(dirstructure[i]); } try { tempsocket.close(); pwr.close(); } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } // logger.info("用户"+clientIp+"："+username+"执行NLST命令"); pw.println("226 Transfer OK"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 226 Transfer OK"); } catch (Exception e){ pw.println("503 Bad sequence of commands."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 503 Bad sequence of commands."); logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } }else{ pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end NLST //LIST命令 else if(command.toUpperCase().startsWith("LIST")) { logger.info("("+username+") ("+clientIp+")> "+command); if(loginStuts){ try{ pw.println("150 Opening data channel for directory list."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 150 Opening data channel for directory list."); PrintWriter pwr = null; try { pwr= new PrintWriter(tempsocket.getOutputStream(),true); } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } FtpUtil.getDetailList(pwr, dir); try { tempsocket.close(); pwr.close(); } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } // logger.info("用户"+clientIp+"："+username+"执行LIST命令"); pw.println("226 Transfer OK"); pw.flush(); logger.info("("+username+") ("+clientIp+")> 226 Transfer OK"); } catch (Exception e){ pw.println("503 Bad sequence of commands."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 503 Bad sequence of commands."); logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } else { pw.println(LOGIN_WARNING); pw.flush(); logger.info("("+username+") ("+clientIp+")> "+LOGIN_WARNING); } } //end LIST // 输入非法命令 else{ logger.info("("+username+") ("+clientIp+")> "+command); pw.println("500 Syntax error, command unrecognized."); pw.flush(); logger.info("("+username+") ("+clientIp+")> 500 Syntax error, command unrecognized."); } } //end while try { logger.info("("+username+") ("+clientIp+")> disconnected."); // logger.info("用户"+clientIp+"："+username+"退出"); br.close(); socketClient.close(); pw.close(); if(null != tempsocket){ tempsocket.close(); } } catch (IOException e) { logger.error(e.getMessage()); for(StackTraceElement ste : e.getStackTrace()){ logger.error(ste.toString()); } } } } import java.io.File; import java.io.PrintWriter; import java.text.SimpleDateFormat; import java.util.Date; /** * FTP工具类 * @author Leon * */ public class FtpUtil { public static void getDetailList(PrintWriter pw, String path){ File dir = new File(path); if (!dir.isDirectory()) { pw.println("500 No such file or directory./r/n"); } File[] files = dir.listFiles(); String modifyDate; for (int i = 0; i < files.length; i++) { modifyDate = new SimpleDateFormat("yyyy/MM/dd hh:mm:ss") .format(new Date(files[i].lastModified())); if (files[i].isDirectory()) { pw.println("drwxr-xr-x ftp ftp 0 " + modifyDate + " " + files[i].getName()); } else { pw.println("-rw-r-r--1 ftp ftp " + files[i].length() + " " + modifyDate + " " + files[i].getName()); } pw.flush(); } pw.println("total:" + files.length); } } ### set log levels ### log4j.logger.com =debug,stdout,D,E ### 输出到控制台 ### log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.Target=System.out log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern = %d{ABSOLUTE} %5p %c{1}:%L - %m%n ## 输出DEBUG级别以上的日志 log4j.appender.D=org.apache.log4j.DailyRollingFileAppender log4j.appender.D.File=c:/logs/logs.log log4j.appender.D.Append =true ## 输出DEBUG级别以上的日志 log4j.appender.D.Threshold=DEBUG log4j.appender.D.layout=org.apache.log4j.PatternLayout log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] - [ %p ] %m%n ### 保存异常信息到单独文件 ### log4j.appender.E=org.apache.log4j.DailyRollingFileAppender ## 异常日志文件名 log4j.appender.E.File=c:/logs/errors.log log4j.appender.E.Append=true ## 只输出ERROR级别以上的日志!!! log4j.appender.E.Threshold=ERROR log4j.appender.E.layout=org.apache.log4j.PatternLayout log4j.appender.E.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] - [ %p ] %m%n 以上内容是小编给大家介绍的Java实现FTP服务器功能实例代码的相关知识，希望大家喜欢。