summaryrefslogtreecommitdiff
path: root/lib/net/ftp.rb
blob: ca2c00a790652b572ef2c20fc468c3a877959009 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
# 
# = net/ftp.rb - FTP Client Library
# 
# Written by Shugo Maeda <shugo@ruby-lang.org>.
#
# Documentation by Gavin Sinclair, sourced from "Programming Ruby" (Hunt/Thomas)
# and "Ruby In a Nutshell" (Matsumoto), used with permission.
# 
# This library is distributed under the terms of the Ruby license.
# You can freely distribute/modify this library.
#
# It is included in the Ruby standard library.
#
# See the Net::FTP class for an overview.
#

require "socket"
require "monitor"

module Net

  # :stopdoc:
  class FTPError < StandardError; end
  class FTPReplyError < FTPError; end
  class FTPTempError < FTPError; end 
  class FTPPermError < FTPError; end 
  class FTPProtoError < FTPError; end
  # :startdoc:

  #
  # This class implements the File Transfer Protocol.  If you have used a
  # command-line FTP program, and are familiar with the commands, you will be
  # able to use this class easily.  Some extra features are included to take
  # advantage of Ruby's style and strengths.
  #
  # == Example
  # 
  #   require 'net/ftp'
  #
  # === Example 1
  #  
  #   ftp = Net::FTP.new('ftp.netlab.co.jp')
  #   ftp.login
  #   files = ftp.chdir('pub/lang/ruby/contrib')
  #   files = ftp.list('n*')
  #   ftp.getbinaryfile('nif.rb-0.91.gz', 'nif.gz', 1024)
  #   ftp.close
  #
  # === Example 2
  #
  #   Net::FTP.open('ftp.netlab.co.jp') do |ftp|
  #     ftp.login
  #     files = ftp.chdir('pub/lang/ruby/contrib')
  #     files = ftp.list('n*')
  #     ftp.getbinaryfile('nif.rb-0.91.gz', 'nif.gz', 1024)
  #   end
  #
  # == Major Methods
  #
  # The following are the methods most likely to be useful to users:
  # - FTP.open
  # - #getbinaryfile
  # - #gettextfile
  # - #putbinaryfile
  # - #puttextfile
  # - #chdir
  # - #nlst
  # - #size
  # - #rename
  # - #delete
  #
  class FTP
    include MonitorMixin
    
    # :stopdoc:
    FTP_PORT = 21
    CRLF = "\r\n"
    DEFAULT_BLOCKSIZE = 4096
    # :startdoc:
    
    # When +true+, transfers are performed in binary mode.  Default: +true+.
    attr_accessor :binary

    # When +true+, the connection is in passive mode.  Default: +false+.
    attr_accessor :passive

    # When +true+, all traffic to and from the server is written
    # to +$stdout+.  Default: +false+.
    attr_accessor :debug_mode

    # Sets or retrieves the +resume+ status, which decides whether incomplete
    # transfers are resumed or restarted.  Default: +false+.
    attr_accessor :resume

    # The server's welcome message.
    attr_reader :welcome

    # The server's last response code.
    attr_reader :last_response_code
    alias lastresp last_response_code

    # The server's last response.
    attr_reader :last_response
    
    #
    # A synonym for <tt>FTP.new</tt>, but with a mandatory host parameter.
    #
    # If a block is given, it is passed the +FTP+ object, which will be closed
    # when the block finishes, or when an exception is raised.
    #
    def FTP.open(host, user = nil, passwd = nil, acct = nil)
      if block_given?
        ftp = new(host, user, passwd, acct)
        begin
          yield ftp
        ensure
          ftp.close
        end
      else
        new(host, user, passwd, acct)
      end
    end
    
    #
    # Creates and returns a new +FTP+ object. If a +host+ is given, a connection
    # is made. Additionally, if the +user+ is given, the given user name,
    # password, and (optionally) account are used to log in.  See #login.
    #
    def initialize(host = nil, user = nil, passwd = nil, acct = nil)
      super()
      @binary = true
      @passive = false
      @debug_mode = false
      @resume = false
      if host
	connect(host)
	if user
	  login(user, passwd, acct)
	end
      end
    end

    # Obsolete
    def return_code
      $stderr.puts("warning: Net::FTP#return_code is obsolete and do nothing")
      return "\n"
    end

    # Obsolete
    def return_code=(s)
      $stderr.puts("warning: Net::FTP#return_code= is obsolete and do nothing")
    end

    def open_socket(host, port)
      if defined? SOCKSsocket and ENV["SOCKS_SERVER"]
	@passive = true
	return SOCKSsocket.open(host, port)
      else
	return TCPSocket.open(host, port)
      end
    end
    private :open_socket
    
    #
    # Establishes an FTP connection to host, optionally overriding the default
    # port. If the environment variable +SOCKS_SERVER+ is set, sets up the
    # connection through a SOCKS proxy. Raises an exception (typically
    # <tt>Errno::ECONNREFUSED</tt>) if the connection cannot be established.
    #
    def connect(host, port = FTP_PORT)
      if @debug_mode
	print "connect: ", host, ", ", port, "\n"
      end
      synchronize do
	@sock = open_socket(host, port)
	voidresp
      end
    end

    #
    # WRITEME or make private
    #
    def set_socket(sock, get_greeting = true)
      synchronize do
	@sock = sock
	if get_greeting
	  voidresp
	end
      end
    end

    def sanitize(s)
      if s =~ /^PASS /i
	return s[0, 5] + "*" * (s.length - 5)
      else
	return s
      end
    end
    private :sanitize
    
    def putline(line)
      if @debug_mode
	print "put: ", sanitize(line), "\n"
      end
      line = line + CRLF
      @sock.write(line)
    end
    private :putline
    
    def getline
      line = @sock.readline # if get EOF, raise EOFError
      line.sub!(/(\r\n|\n|\r)\z/n, "")
      if @debug_mode
	print "get: ", sanitize(line), "\n"
      end
      return line
    end
    private :getline
    
    def getmultiline
      line = getline
      buff = line
      if line[3] == ?-
	  code = line[0, 3]
	begin
	  line = getline
	  buff << "\n" << line
	end until line[0, 3] == code and line[3] != ?-
      end
      return buff << "\n"
    end
    private :getmultiline
    
    def getresp
      @last_response = getmultiline
      @last_response_code = @last_response[0, 3]
      case @last_response_code
      when /\A[123]/
	return @last_response
      when /\A4/
	raise FTPTempError, @last_response
      when /\A5/
	raise FTPPermError, @last_response
      else
	raise FTPProtoError, @last_response
      end
    end
    private :getresp
    
    def voidresp
      resp = getresp
      if resp[0] != ?2
	raise FTPReplyError, resp
      end
    end
    private :voidresp
    
    #
    # Sends a command and returns the response.
    #
    def sendcmd(cmd)
      synchronize do
	putline(cmd)
	return getresp
      end
    end
    
    #
    # Sends a command and expect a response beginning with '2'.
    #
    def voidcmd(cmd)
      synchronize do
	putline(cmd)
	voidresp
      end
    end
    
    def sendport(host, port)
      af = (@sock.peeraddr)[0]
      if af == "AF_INET"
	cmd = "PORT " + (host.split(".") + port.divmod(256)).join(",")
      elsif af == "AF_INET6"
	cmd = sprintf("EPRT |2|%s|%d|", host, port)
      else
	raise FTPProtoError, host
      end
      voidcmd(cmd)
    end
    private :sendport
    
    def makeport
      sock = TCPServer.open(@sock.addr[3], 0)
      port = sock.addr[1]
      host = sock.addr[3]
      resp = sendport(host, port)
      return sock
    end
    private :makeport
    
    def makepasv
      if @sock.peeraddr[0] == "AF_INET"
	host, port = parse227(sendcmd("PASV"))
      else
	host, port = parse229(sendcmd("EPSV"))
	#     host, port = parse228(sendcmd("LPSV"))
      end
      return host, port
    end
    private :makepasv
    
    def transfercmd(cmd, rest_offset = nil)
      if @passive
	host, port = makepasv
	conn = open_socket(host, port)
	if @resume and rest_offset
	  resp = sendcmd("REST " + rest_offset.to_s) 
	  if resp[0] != ?3
	    raise FTPReplyError, resp
	  end
	end
	resp = sendcmd(cmd)
        # skip 2XX for some ftp servers
        resp = getresp if resp[0] == ?2
	if resp[0] != ?1
	  raise FTPReplyError, resp
	end
      else
	sock = makeport
	if @resume and rest_offset
	  resp = sendcmd("REST " + rest_offset.to_s) 
	  if resp[0] != ?3
	    raise FTPReplyError, resp
	  end
	end
	resp = sendcmd(cmd)
        # skip 2XX for some ftp servers
        resp = getresp if resp[0] == ?2
	if resp[0] != ?1
	  raise FTPReplyError, resp
	end
	conn = sock.accept
	sock.close
      end
      return conn
    end
    private :transfercmd
    
    def getaddress
      thishost = Socket.gethostname
      if not thishost.index(".")
	thishost = Socket.gethostbyname(thishost)[0]
      end
      if ENV.has_key?("LOGNAME")
	realuser = ENV["LOGNAME"]
      elsif ENV.has_key?("USER")
	realuser = ENV["USER"]
      else
	realuser = "anonymous"
      end
      return realuser + "@" + thishost
    end
    private :getaddress
    
    #
    # Logs in to the remote host. The session must have been previously
    # connected.  If +user+ is the string "anonymous" and the +password+ is
    # +nil+, a password of <tt>user@host</tt> is synthesized. If the +acct+
    # parameter is not +nil+, an FTP ACCT command is sent following the
    # successful login.  Raises an exception on error (typically
    # <tt>Net::FTPPermError</tt>).
    #
    def login(user = "anonymous", passwd = nil, acct = nil)
      if user == "anonymous" and passwd == nil
	passwd = getaddress
      end
      
      resp = ""
      synchronize do
	resp = sendcmd('USER ' + user)
	if resp[0] == ?3
	  resp = sendcmd('PASS ' + passwd)
	end
	if resp[0] == ?3
	  resp = sendcmd('ACCT ' + acct)
	end
      end
      if resp[0] != ?2
	raise FTPReplyError, resp
      end
      @welcome = resp
    end
    
    #
    # Puts the connection into binary (image) mode, issues the given command,
    # and fetches the data returned, passing it to the associated block in
    # chunks of +blocksize+ characters. Note that +cmd+ is a server command
    # (such as "RETR myfile").
    #
    def retrbinary(cmd, blocksize, rest_offset = nil) # :yield: data
      synchronize do
	voidcmd("TYPE I")
	conn = transfercmd(cmd, rest_offset)
	loop do
	  data = conn.read(blocksize)
	  break if data == nil
	  yield(data)
	end
	conn.close
	voidresp
      end
    end
    
    #
    # Puts the connection into ASCII (text) mode, issues the given command, and
    # passes the resulting data, one line at a time, to the associated block. If
    # no block is given, prints the lines. Note that +cmd+ is a server command
    # (such as "RETR myfile").
    #
    def retrlines(cmd) # :yield: line
      synchronize do
	voidcmd("TYPE A")
	conn = transfercmd(cmd)
	loop do
	  line = conn.gets
	  break if line == nil
	  if line[-2, 2] == CRLF
	    line = line[0 .. -3]
	  elsif line[-1] == ?\n
	    line = line[0 .. -2]
	  end
	  yield(line)
	end
	conn.close
	voidresp
      end
    end
    
    #
    # Puts the connection into binary (image) mode, issues the given server-side
    # command (such as "STOR myfile"), and sends the contents of the file named
    # +file+ to the server. If the optional block is given, it also passes it
    # the data, in chunks of +blocksize+ characters.
    #
    def storbinary(cmd, file, blocksize, rest_offset = nil, &block) # :yield: data
      if rest_offset
        file.seek(rest_offset, IO::SEEK_SET)
      end
      synchronize do
	voidcmd("TYPE I")
	conn = transfercmd(cmd, rest_offset)
	loop do
	  buf = file.read(blocksize)
	  break if buf == nil
	  conn.write(buf)
	  yield(buf) if block
	end
	conn.close
	voidresp
      end
    end
    
    #
    # Puts the connection into ASCII (text) mode, issues the given server-side
    # command (such as "STOR myfile"), and sends the contents of the file
    # named +file+ to the server, one line at a time. If the optional block is
    # given, it also passes it the lines.
    #
    def storlines(cmd, file, &block) # :yield: line
      synchronize do
	voidcmd("TYPE A")
	conn = transfercmd(cmd)
	loop do
	  buf = file.gets
	  break if buf == nil
	  if buf[-2, 2] != CRLF
	    buf = buf.chomp + CRLF
	  end
	  conn.write(buf)
	  yield(buf) if block
	end
	conn.close
	voidresp
      end
    end

    #
    # Retrieves +remotefile+ in binary mode, storing the result in +localfile+.
    # If a block is supplied, it is passed the retrieved data in +blocksize+
    # chunks.
    #
    def getbinaryfile(remotefile, localfile = File.basename(remotefile),
		      blocksize = DEFAULT_BLOCKSIZE, &block) # :yield: data
      if @resume
	rest_offset = File.size?(localfile)
	f = open(localfile, "a")
      else
	rest_offset = nil
	f = open(localfile, "w")
      end
      begin
	f.binmode
	retrbinary("RETR " + remotefile, blocksize, rest_offset) do |data|
	  f.write(data)
	  yield(data) if block
	end
      ensure
	f.close
      end
    end
    
    #
    # Retrieves +remotefile+ in ASCII (text) mode, storing the result in
    # +localfile+. If a block is supplied, it is passed the retrieved data one
    # line at a time.
    #
    def gettextfile(remotefile, localfile = File.basename(remotefile), &block) # :yield: line
      f = open(localfile, "w")
      begin
	retrlines("RETR " + remotefile) do |line|
	  f.puts(line)
	  yield(line) if block
	end
      ensure
	f.close
      end
    end

    #
    # Retrieves +remotefile+ in whatever mode the session is set (text or
    # binary).  See #gettextfile and #getbinaryfile.
    #
    def get(remotefile, localfile = File.basename(remotefile),
	    blocksize = DEFAULT_BLOCKSIZE, &block) # :yield: data
      unless @binary
	gettextfile(remotefile, localfile, &block)
      else
	getbinaryfile(remotefile, localfile, blocksize, &block)
      end
    end
    
    #
    # Transfers +localfile+ to the server in binary mode, storing the result in
    # +remotefile+. If a block is supplied, calls it, passing in the transmitted
    # data in +blocksize+ chunks.
    #
    def putbinaryfile(localfile, remotefile = File.basename(localfile),
		      blocksize = DEFAULT_BLOCKSIZE, &block) # :yield: data
      if @resume
        begin
          rest_offset = size(remotefile)
        rescue Net::FTPPermError
          rest_offset = nil
        end
      else
	rest_offset = nil
      end
      f = open(localfile)
      begin
	f.binmode
	storbinary("STOR " + remotefile, f, blocksize, rest_offset, &block)
      ensure
	f.close
      end
    end
    
    #
    # Transfers +localfile+ to the server in ASCII (text) mode, storing the result
    # in +remotefile+. If callback or an associated block is supplied, calls it,
    # passing in the transmitted data one line at a time.
    #
    def puttextfile(localfile, remotefile = File.basename(localfile), &block) # :yield: line
      f = open(localfile)
      begin
	storlines("STOR " + remotefile, f, &block)
      ensure
	f.close
      end
    end

    #
    # Transfers +localfile+ to the server in whatever mode the session is set
    # (text or binary).  See #puttextfile and #putbinaryfile.
    #
    def put(localfile, remotefile = File.basename(localfile),
	    blocksize = DEFAULT_BLOCKSIZE, &block)
      unless @binary
	puttextfile(localfile, remotefile, &block)
      else
	putbinaryfile(localfile, remotefile, blocksize, &block)
      end
    end

    #
    # Sends the ACCT command.  TODO: more info.
    #
    def acct(account)
      cmd = "ACCT " + account
      voidcmd(cmd)
    end
    
    #
    # Returns an array of filenames in the remote directory.
    #
    def nlst(dir = nil)
      cmd = "NLST"
      if dir
	cmd = cmd + " " + dir
      end
      files = []
      retrlines(cmd) do |line|
	files.push(line)
      end
      return files
    end
    
    #
    # Returns an array of file information in the directory (the output is like
    # `ls -l`).  If a block is given, it iterates through the listing.
    #
    def list(*args, &block) # :yield: line
      cmd = "LIST"
      args.each do |arg|
	cmd = cmd + " " + arg
      end
      if block
	retrlines(cmd, &block)
      else
	lines = []
	retrlines(cmd) do |line|
	  lines << line
	end
	return lines
      end
    end
    alias ls list
    alias dir list
    
    #
    # Renames a file on the server.
    #
    def rename(fromname, toname)
      resp = sendcmd("RNFR " + fromname)
      if resp[0] != ?3
	raise FTPReplyError, resp
      end
      voidcmd("RNTO " + toname)
    end
    
    #
    # Deletes a file on the server.
    #
    def delete(filename)
      resp = sendcmd("DELE " + filename)
      if resp[0, 3] == "250"
	return
      elsif resp[0] == ?5
	raise FTPPermError, resp
      else
	raise FTPReplyError, resp
      end
    end
    
    #
    # Changes the (remote) directory.
    #
    def chdir(dirname)
      if dirname == ".."
	begin
	  voidcmd("CDUP")
	  return
	rescue FTPPermError
	  if $![0, 3] != "500"
	    raise FTPPermError, $!
	  end
	end
      end
      cmd = "CWD " + dirname
      voidcmd(cmd)
    end
    
    #
    # Returns the size of the given (remote) filename.
    #
    def size(filename)
      voidcmd("TYPE I")
      resp = sendcmd("SIZE " + filename)
      if resp[0, 3] != "213" 
	raise FTPReplyError, resp
      end
      return resp[3..-1].strip.to_i
    end
    
    MDTM_REGEXP = /^(\d\d\d\d)(\d\d)(\d\d)(\d\d)(\d\d)(\d\d)/  # :nodoc:
    
    #
    # Returns the last modification time of the (remote) file.  If +local+ is
    # +true+, it is returned as a local time, otherwise it's a UTC time.
    #
    def mtime(filename, local = false)
      str = mdtm(filename)
      ary = str.scan(MDTM_REGEXP)[0].collect {|i| i.to_i}
      return local ? Time.local(*ary) : Time.gm(*ary)
    end
    
    #
    # Creates a remote directory.
    #
    def mkdir(dirname)
      resp = sendcmd("MKD " + dirname)
      return parse257(resp)
    end
    
    #
    # Removes a remote directory.
    #
    def rmdir(dirname)
      voidcmd("RMD " + dirname)
    end
    
    #
    # Returns the current remote directory.
    #
    def pwd
      resp = sendcmd("PWD")
      return parse257(resp)
    end
    alias getdir pwd
    
    #
    # Returns system information.
    #
    def system
      resp = sendcmd("SYST")
      if resp[0, 3] != "215"
	raise FTPReplyError, resp
      end
      return resp[4 .. -1]
    end
    
    #
    # Aborts the previous command (ABOR command).
    #
    def abort
      line = "ABOR" + CRLF
      print "put: ABOR\n" if @debug_mode
      @sock.send(line, Socket::MSG_OOB)
      resp = getmultiline
      unless ["426", "226", "225"].include?(resp[0, 3])
	raise FTPProtoError, resp
      end
      return resp
    end
    
    #
    # Returns the status (STAT command).
    #
    def status
      line = "STAT" + CRLF
      print "put: STAT\n" if @debug_mode
      @sock.send(line, Socket::MSG_OOB)
      return getresp
    end
    
    #
    # Issues the MDTM command.  TODO: more info.
    #
    def mdtm(filename)
      resp = sendcmd("MDTM " + filename)
      if resp[0, 3] == "213"
	return resp[3 .. -1].strip
      end
    end
    
    #
    # Issues the HELP command.
    #
    def help(arg = nil)
      cmd = "HELP"
      if arg
	cmd = cmd + " " + arg
      end
      sendcmd(cmd)
    end
    
    #
    # Exits the FTP session.
    #
    def quit
      voidcmd("QUIT")
    end

    #
    # Issues a NOOP command.
    #
    def noop
      voidcmd("NOOP")
    end

    #
    # Issues a SITE command.
    #
    def site(arg)
      cmd = "SITE " + arg
      voidcmd(cmd)
    end
    
    #
    # Closes the connection.  Further operations are impossible until you open
    # a new connection with #connect.
    #
    def close
      @sock.close if @sock and not @sock.closed?
    end
    
    #
    # Returns +true+ iff the connection is closed.
    #
    def closed?
      @sock == nil or @sock.closed?
    end
    
    def parse227(resp)
      if resp[0, 3] != "227"
	raise FTPReplyError, resp
      end
      left = resp.index("(")
      right = resp.index(")")
      if left == nil or right == nil
	raise FTPProtoError, resp
      end
      numbers = resp[left + 1 .. right - 1].split(",")
      if numbers.length != 6
	raise FTPProtoError, resp
      end
      host = numbers[0, 4].join(".")
      port = (numbers[4].to_i << 8) + numbers[5].to_i
      return host, port
    end
    private :parse227
    
    def parse228(resp)
      if resp[0, 3] != "228"
	raise FTPReplyError, resp
      end
      left = resp.index("(")
      right = resp.index(")")
      if left == nil or right == nil
	raise FTPProtoError, resp
      end
      numbers = resp[left + 1 .. right - 1].split(",")
      if numbers[0] == "4"
	if numbers.length != 9 || numbers[1] != "4" || numbers[2 + 4] != "2"
	  raise FTPProtoError, resp
	end
	host = numbers[2, 4].join(".")
	port = (numbers[7].to_i << 8) + numbers[8].to_i
      elsif numbers[0] == "6"
	if numbers.length != 21 || numbers[1] != "16" || numbers[2 + 16] != "2"
	  raise FTPProtoError, resp
	end
	v6 = ["", "", "", "", "", "", "", ""]
	for i in 0 .. 7
	  v6[i] = sprintf("%02x%02x", numbers[(i * 2) + 2].to_i,
			  numbers[(i * 2) + 3].to_i)
	end
	host = v6[0, 8].join(":")
	port = (numbers[19].to_i << 8) + numbers[20].to_i
      end 
      return host, port
    end
    private :parse228
    
    def parse229(resp)
      if resp[0, 3] != "229"
	raise FTPReplyError, resp
      end
      left = resp.index("(")
      right = resp.index(")")
      if left == nil or right == nil
	raise FTPProtoError, resp
      end
      numbers = resp[left + 1 .. right - 1].split(resp[left + 1, 1])
      if numbers.length != 4
	raise FTPProtoError, resp
      end
      port = numbers[3].to_i
      host = (@sock.peeraddr())[3]
      return host, port
    end
    private :parse229
    
    def parse257(resp)
      if resp[0, 3] != "257"
	raise FTPReplyError, resp
      end
      if resp[3, 2] != ' "'
	return ""
      end
      dirname = ""
      i = 5
      n = resp.length
      while i < n
	c = resp[i, 1]
	i = i + 1
	if c == '"'
	  if i > n or resp[i, 1] != '"'
	    break
	  end
	  i = i + 1
	end
	dirname = dirname + c
      end
      return dirname
    end
    private :parse257
  end

end


# Documentation comments:
#  - sourced from pickaxe and nutshell, with improvements (hopefully)
#  - three methods should be private (search WRITEME)
#  - two methods need more information (search TODO)