Python版本
实现了比之前的xxftp更多更完善的功能 🙂
1、继续支持多用户
2、继续支持虚拟目录
3、增加支持用户根目录以及映射虚拟目录的权限设置
4、增加支持限制用户根目录或者虚拟目录的空间大小

xxftp的特点
1、开源、跨平台
2、简单、易用
3、不需要数据库
4、可扩展性超强
5、你可以免费使用xxftp假设自己的私人FTP服务器

测试地址
ftp://xiaoxia.org
匿名帐号可以使用！
匿名根目录只读，映射了一个虚拟目录，可以上传文件但不允许更改！

使用方法
跟之前用C语言写的xxftp使用方法一样：

1. Create a root directory to hold the user directories.
   Configure it in config.xml.
2. Create user directories under the root directory.
   If you want to specify a password, create a directory named ".xxftp",
   under which create a text file named "password" containing the MD5
   code of the password.
3. If you want to specify the welcome and goodbye message, write it in
   xxftp.welcome and xxftp.goodbye under the root directory.
4. Configure config.xml.

The structure of your FTP server root may be like:

-/root
	-xxftp.welcome
	-xxftp.goodbye

	-user1
		-.xxftp
			-password
		-...
	-user2
		-.xxftp
			-password
		-...
	-anonymous

源代码

import socket, threading, os, sys, time
import hashlib, platform, stat

listen_ip = "localhost"
listen_port = 21
conn_list = []
root_dir = "./home"
max_connections = 500
conn_timeout = 120

class FtpConnection(threading.Thread):
    def __init__(self, fd):
        threading.Thread.__init__(self)
        self.fd = fd
        self.running = True
        self.setDaemon(True)
        self.alive_time = time.time()
        self.option_utf8 = False
        self.identified = False
        self.option_pasv = True
        self.username = ""
    def process(self, cmd, arg):
        cmd = cmd.upper();
        if self.option_utf8:
            arg = unicode(arg, "utf8").encode(sys.getfilesystemencoding())
        print "<<", cmd, arg, self.fd
        # Ftp Command
        if cmd == "BYE" or cmd == "QUIT":
            if os.path.exists(root_dir + "/xxftp.goodbye"):
                self.message(221, open(root_dir + "/xxftp.goodbye").read())
            else:
                self.message(221, "Bye!")
            self.running = False
            return
        elif cmd == "USER":
            # Set Anonymous User
            if arg == "": arg = "anonymous"
            for c in arg:
                if not c.isalpha() and not c.isdigit() and c!="_":
                    self.message(530, "Incorrect username.")
                    return
            self.username = arg
            self.home_dir = root_dir + "/" + self.username
            self.curr_dir = "/"
            self.curr_dir, self.full_path, permission, self.vdir_list, \
                limit_size, is_virtual = self.parse_path("/")
            if not os.path.isdir(self.home_dir):
                self.message(530, "User " + self.username + " not exists.")
                return
            self.pass_path = self.home_dir + "/.xxftp/password"
            if os.path.isfile(self.pass_path):
                self.message(331, "Password required for " + self.username)
            else:
                self.message(230, "Identified!")
                self.identified = True
            return
        elif cmd == "PASS":
            if open(self.pass_path).read() == hashlib.md5(arg).hexdigest():
                self.message(230, "Identified!")
                self.identified = True
            else:
                self.message(530, "Not identified!")
                self.identified = False
            return
        elif not self.identified:
            self.message(530, "Please login with USER and PASS.")
            return

        self.alive_time = time.time()
        finish = True
        if cmd == "NOOP":
            self.message(200, "ok")
        elif cmd == "TYPE":
            self.message(200, "ok")
        elif cmd == "SYST":
            self.message(200, "UNIX")
        elif cmd == "EPSV" or cmd == "PASV":
            self.option_pasv = True
            try:
                self.data_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                self.data_fd.bind((listen_ip, 0))
                self.data_fd.listen(1)
                ip, port = self.data_fd.getsockname()
                if cmd == "EPSV":
                    self.message(229, "Entering Extended Passive Mode (|||" + str(port) + "|)")
                else:
                    ipnum = socket.inet_aton(ip)
                    self.message(227, "Entering Passive Mode (%s,%u,%u)." %
                        (",".join(ip.split(".")), (port>>8&0xff), (port&0xff)))
            except:
                self.message(500, "failed to create data socket.")
        elif cmd == "EPRT":
            self.message(500, "implement EPRT later...")
        elif cmd == "PORT":
            self.option_pasv = False
            self.data_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s = arg.split(",")
            self.data_ip = ".".join(s[:4])
            self.data_port = int(s[4])*256 + int(s[5])
            self.message(200, "ok")
        elif cmd == "PWD" or cmd == "XPWD":
            if self.curr_dir == "": self.curr_dir = "/"
            self.message(257, '"' + self.curr_dir + '"')
        elif cmd == "LIST" or cmd == "NLST":
            if arg != "" and arg[0] == "-": arg = "" # omit parameters
            remote, local, perm, vdir_list, limit_size, is_virtual = self.parse_path(arg)
            if not os.path.exists(local):
                self.message(550, "failed.")
                return
            if not self.establish(): return
            self.message(150, "ok")
            for v in vdir_list:
                f = v[0]
                if self.option_utf8:
                    f = unicode(f, sys.getfilesystemencoding()).encode("utf8")
                if cmd == "NLST":
                    info = f + "\r\n"
                else:
                    info = "d%s%s------- %04u %8s %8s %8lu %s %s\r\n" % (
                        "r" if "read" in perm else "-",
                        "w" if "write" in perm else "-",
                        1, "0", "0", 0,
                        time.strftime("%b %d  %Y", time.localtime(time.time())),
                        f)
                self.data_fd.send(info)
            for f in os.listdir(local):
                if f[0] == ".": continue
                path = local + "/" + f
                if self.option_utf8:
                    f = unicode(f, sys.getfilesystemencoding()).encode("utf8")
                if cmd == "NLST":
                    info = f + "\r\n"
                else:
                    st = os.stat(path)
                    info = "%s%s%s------- %04u %8s %8s %8lu %s %s\r\n" % (
                        "-" if os.path.isfile(path) else "d",
                        "r" if "read" in perm else "-",
                        "w" if "write" in perm else "-",
                        1, "0", "0", st[stat.ST_SIZE],
                        time.strftime("%b %d  %Y", time.localtime(st[stat.ST_MTIME])),
                        f)
                self.data_fd.send(info)
            self.message(226, "Limit size: " + str(limit_size))
            self.data_fd.close()
            self.data_fd = 0
        elif cmd == "REST":
            self.file_pos = int(arg)
            self.message(250, "ok")
        elif cmd == "FEAT":
            features = "211-Features:\r\nSITES\r\nEPRT\r\nEPSV\r\nMDTM\r\nPASV\r\n"\
                "REST STREAM\r\nSIZE\r\nUTF8\r\n211 End\r\n"
            self.fd.send(features)
        elif cmd == "OPTS":
            arg = arg.upper()
            if arg == "UTF8 ON":
                self.option_utf8 = True
                self.message(200, "ok")
            elif arg == "UTF8 OFF":
                self.option_utf8 = False
                self.message(200, "ok")
            else:
                self.message(500, "unrecognized option")
        elif cmd == "CDUP":
            finish = False
            arg = ".."
        else:
            finish = False
        if finish: return
        # Parse argument ( It's a path )
        if arg == "":
            self.message(500, "where's my argument?")
            return
        remote, local, permission, vdir_list, limit_size, is_virtual = \
            self.parse_path(arg)
        # can not do anything to virtual directory
        if is_virtual: permission = "none"
        can_read, can_write, can_modify = "read" in permission, "write" in permission, "modify" in permission
        newpath = local
        try:
            if cmd == "CWD":
                if(os.path.isdir(newpath)):
                    self.curr_dir = remote
                    self.full_path = newpath
                    self.message(250, '"' + remote + '"')
                else:
                    self.message(550, "failed")
            elif cmd == "MDTM":
                if os.path.exists(newpath):
                    self.message(213, time.strftime("%Y%m%d%I%M%S", time.localtime(
                        os.path.getmtime(newpath))))
                else:
                    self.message(550, "failed")
            elif cmd == "SIZE":
                self.message(231, os.path.getsize(newpath))
            elif cmd == "XMKD" or cmd == "MKD":
                if not can_modify:
                    self.message(550, "permission denied.")
                    return
                os.mkdir(newpath)
                self.message(250, "ok")
            elif cmd == "RNFR":
                if not can_modify:
                    self.message(550, "permission denied.")
                    return
                self.temp_path = newpath
                self.message(350, "rename from " + remote)
            elif cmd == "RNTO":
                os.rename(self.temp_path, newpath)
                self.message(250, "RNTO to " + remote)
            elif cmd == "XRMD" or cmd == "RMD":
                if not can_modify:
                    self.message(550, "permission denied.")
                    return
                os.rmdir(newpath)
                self.message(250, "ok")
            elif cmd == "DELE":
                if not can_modify:
                    self.message(550, "permission denied.")
                    return
                os.remove(newpath)
                self.message(250, "ok")
            elif cmd == "RETR":
                if not os.path.isfile(newpath):
                    self.message(550, "failed")
                    return
                if not can_read:
                    self.message(550, "permission denied.")
                    return
                if not self.establish(): return
                self.message(150, "ok")
                f = open(newpath, "rb")
                while self.running:
                    self.alive_time = time.time()
                    data = f.read(8192)
                    if len(data) == 0: break
                    self.data_fd.send(data)
                f.close()
                self.data_fd.close()
                self.data_fd = 0
                self.message(226, "ok")
            elif cmd == "STOR" or cmd == "APPE":
                if not can_write:
                    self.message(550, "permission denied.")
                    return
                if os.path.exists(newpath) and not can_modify:
                    self.message(550, "permission denied.")
                    return
                # Check space size remained!
                used_size = 0
                if limit_size > 0:
                    used_size = self.get_dir_size(os.path.dirname(newpath))
                if not self.establish(): return
                self.message(150, "ok")
                f = open(newpath, ("ab" if cmd == "APPE" else "wb") )
                while self.running:
                    self.alive_time = time.time()
                    data = self.data_fd.recv(8192)
                    if len(data) == 0: break
                    if limit_size > 0:
                        used_size = used_size + len(data)
                        if used_size > limit_size: break
                    f.write(data)
                f.close()
                self.data_fd.close()
                self.data_fd = 0
                if limit_size > 0 and used_size > limit_size:
                    self.message(550, "Exceeding user space limit: " + str(limit_size) + " bytes")
                else:
                    self.message(226, "ok")
            else:
                self.message(500, cmd + " not implemented")
        except:
            self.message(550, "failed.")
    
    def establish(self):
        if self.data_fd == 0:
            self.message(500, "no data connection")
            return False
        if self.option_pasv:
            fd = self.data_fd.accept()[0]
            self.data_fd.close()
            self.data_fd = fd
        else:
            try:
                self.data_fd.connect((self.data_ip, self.data_port))
            except:
                self.message(500, "failed to establish data connection")
                return False
        return True

    def read_virtual(self, path):
        vdir_list = []
        path = path + "/.xxftp/virtual"
        if os.path.isfile(path):
            for v in open(path, "r").readlines():
                items = v.split()
                items[1] = items[1].replace("$root", root_dir)
                vdir_list.append(items)
        return vdir_list

    def get_dir_size(self, folder):
        size = 0
        for path, dirs, files in os.walk(folder):
            for f in files:
                size += os.path.getsize(os.path.join(path, f))
        return size
    
    def read_size(self, path):
        size = 0
        path = path + "/.xxftp/size"
        if os.path.isfile(path):
            size = int(open(path, "r").readline())
        return size

    def read_permission(self, path):
        permission = "read,write,modify"
        path = path + "/.xxftp/permission"
        if os.path.isfile(path):
            permission = open(path, "r").readline()
        return permission
    
    def parse_path(self, path):
        if path == "": path = "."
        if path[0] != "/":
            path = self.curr_dir + "/" + path
        s = os.path.normpath(path).replace("\\", "/").split("/")
        local = self.home_dir
        # reset directory permission
        vdir_list = self.read_virtual(local)
        limit_size = self.read_size(local)
        permission = self.read_permission(local)
        remote = ""
        is_virtual = False
        for name in s:
            name = name.lstrip(".")
            if name == "": continue
            remote = remote + "/" + name
            is_virtual = False
            for v in vdir_list:
                if v[0] == name:
                    permission = v[2]
                    local = v[1]
                    limit_size = self.read_size(local)
                    is_virtual = True
            if not is_virtual: local = local + "/" + name
            vdir_list = self.read_virtual(local)
        return (remote, local, permission, vdir_list, limit_size, is_virtual)

    def run(self):
        ''' Connection Process '''
        try:
            if len(conn_list) > max_connections:
                self.message(500, "too many connections!")
                self.fd.close()
                self.running = False
                return
            # Welcome Message
            if os.path.exists(root_dir + "/xxftp.welcome"):
                self.message(220, open(root_dir + "/xxftp.welcome").read())
            else:
                self.message(220, "xxftp(Python) www.xiaoxia.org")
            # Command Loop
            line = ""
            while self.running:
                data = self.fd.recv(4096)
                if len(data) == 0: break
                line += data
                if line[-2:] != "\r\n": continue
                line = line[:-2]
                space = line.find(" ")
                if space == -1:
                    self.process(line, "")
                else:
                    self.process(line[:space], line[space+1:])
                line = ""
        except:
            print "error", sys.exc_info()
        self.running = False
        self.fd.close()
        print "connection end", self.fd, "user", self.username

    def message(self, code, s):
        ''' Send Ftp Message '''
        s = str(s).replace("\r", "")
        ss = s.split("\n")
        if len(ss) > 1:
            r = (str(code) + "-") + ("\r\n" + str(code) + "-").join(ss[:-1])
            r += "\r\n" + str(code) + " " + ss[-1] + "\r\n"
        else:
            r = str(code) + " " + ss[0] + "\r\n"
        if self.option_utf8:
            r = unicode(r, sys.getfilesystemencoding()).encode("utf8")
        self.fd.send(r)

def server_listen():
    global conn_list
    listen_fd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    listen_fd.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    listen_fd.bind((listen_ip, listen_port))
    listen_fd.listen(1024)
    conn_lock = threading.Lock()
    print "ftpd is listening on ", listen_ip + ":" + str(listen_port)

    while True:
        conn_fd, remote_addr = listen_fd.accept()
        print "connection from ", remote_addr, "conn_list", len(conn_list)
        conn = FtpConnection(conn_fd)
        conn.start()

        conn_lock.acquire()
        conn_list.append(conn)
        # check timeout
        try:
            curr_time = time.time()
            for conn in conn_list:
                if int(curr_time - conn.alive_time) > conn_timeout:
                    if conn.running == True:
                        conn.fd.shutdown(socket.SHUT_RDWR)
                    conn.running = False
            conn_list = [conn for conn in conn_list if conn.running]
        except:
            print sys.exc_info()
        conn_lock.release()


def main():
    server_listen()
    
if __name__ == "__main__":
    main()