第一个 Erlang 程序: Ftp 下载客户端

学习 Erlang 一周的习作:

 1 -module(ftp_down).
 2 -export([get/6,test/0,get_data/4]).
 3 
 4 test() ->
 5 get("ftp.ftpplanet.com", 21, "anonymous", "anonymous", "images/image001_42.jpg", "d:/").
 6 
 7 client_message(Format, Data) ->
 8 io:format("C: "++Format ++"~n", Data).
 9 
 10 server_message(Format, Data) ->
 11 io:format("S: "++Format ++"~n", Data).
 12 
 13 server_verify_message(Data, ExpectedCode) ->
 14 {Code, Message} =Data,
 15 ExpectedCode =Code,
 16 io:format("S: ~s~n", [Message]),
 17 ok.
 18 
 19 recv_until_EOL(Sock, StrSoFar) ->
 20 Len =string:len(StrSoFar),
 21 NotALine =Len <2orelse notstring:equal("\r\n", string:substr(StrSoFar, Len -1, 2)),
 22 if
 23 NotALine ->
 24 {ok, Msg} =gen_tcp:recv(Sock, 1),
 25 recv_until_EOL(Sock, StrSoFar ++Msg);
 26 true->
 27 StrSoFar
 28 end.
 29 
 30 recv_until_EOL(Sock) ->
 31 recv_until_EOL(Sock, "").
 32 
 33 recv_until_xxxend(Sock, Num, Line, LinesSoFar) ->
 34 ExpectedTail =integer_to_list(Num) ++" end",
 35 ExpectedTailLen =string:len(ExpectedTail),
 36 Pos =string:len(Line) -ExpectedTailLen -1,
 37 Eq =Pos >0andalso string:equal(ExpectedTail, string:to_lower(string:substr(Line, Pos, ExpectedTailLen))),
 38 if
 39 Eq ->
 40 {Num, LinesSoFar ++Line};
 41 true->
 42 recv_response(Sock, Num, LinesSoFar ++Line)
 43 end.
 44 
 45 recv_response(Sock, LinesSoFar) ->
 46 Line =recv_until_EOL(Sock),
 47 {Num, [H | _]} =string:to_integer(Line),
 48 if
 49 H ==$-->
 50 recv_until_xxxend(Sock, Num, Line, LinesSoFar);
 51 true->
 52 {Num, LinesSoFar ++Line}
 53 end.
 54 
 55 recv_response(Sock, ResponseNo, LinesSoFar) ->
 56 Line =recv_until_EOL(Sock),
 57 recv_until_xxxend(Sock, ResponseNo, Line, LinesSoFar).
 58 
 59 recv_response(Sock) ->
 60 recv_response(Sock, []).
 61 
 62 send_command(Sock, Msg) ->
 63  ok =gen_tcp:send(Sock, Msg ++"\r\n"),
 64  client_message("~s", [Msg]).
 65  
 66 parse_pasv(Msg) ->
 67 Index1=string:chr(Msg, $(),
 68 Index2=string:chr(Msg, $)),
 69 [A1, A2, A3, A4, B1, B2] =lists:map(fun(S) ->string:strip(S) end, string:tokens(string:substr(Msg, Index1+1, Index2-Index1-1), ",")),
 70 {Nb1, _} =string:to_integer(B1),
 71 {Nb2, _} =string:to_integer(B2),
 72 <<Port:16>>=<<Nb1:8, Nb2:8>>,
 73 {lists:append([A1, ".", A2, ".", A3, ".", A4]), Port}.
 74 
 75 
 76 recv_until_transfer_complete(Sock, {ok , Msg}, MsgSoFar) ->
 77 if
 78 length(Msg) >0->
 79 recv_until_transfer_complete(Sock, gen_tcp:recv(Sock, 0), MsgSoFar ++Msg);
 80 true->
 81 receive
 82 transfer_complete->
 83 MsgSoFar
 84 after200->
 85 recv_until_transfer_complete(Sock, gen_tcp:recv(Sock, 0), MsgSoFar ++Msg)
 86 end
 87 end;
 88 
 89 
 90 recv_until_transfer_complete(_, {error , closed}, MsgSoFar) ->
 91 MsgSoFar.
 92 
 93 recv_until_transfer_complete(Sock) ->
 94 receive
 95 start_transfer->
 96 recv_until_transfer_complete(Sock, gen_tcp:recv(Sock, 0), [])
 97 after30000->
 98 "150 timeout"
 99 end.
 100 
 101 get_data(Addr, Port, LocalFilePath, Control) ->
 102 {ok, DataSock} =gen_tcp:connect(Addr, Port, [{active, false}]),
 103 Data =recv_until_transfer_complete(DataSock),
 104 client_message("<I GOT>: ~wBytes~n", [length(Data)]),
 105 file:write_file(LocalFilePath, list_to_binary(Data)),
 106 gen_tcp:close(DataSock),
 107 Control !bye.
 108 
 109 
 110 get(Host, Port, User, Pass, FilePath, LocalPath) ->
 111 Slash =string:rchr(FilePath, $/),
 112 Path =string:left(FilePath, Slash -1),
 113 File =string:right(FilePath, string:len(FilePath) -Slash),
 114 
 115 {ok, Sock} =gen_tcp:connect(Host, Port, [{active, false}]),
 116 client_message("connect to ~s:~wok.", [Host, Port]),
 117 server_verify_message(recv_response(Sock), 220),
 118 send_command(Sock, "USER "++User),
 119 server_verify_message(recv_response(Sock), 331),
 120 send_command(Sock, "PASS "++Pass),
 121 server_verify_message(recv_response(Sock), 230),
 122 send_command(Sock, "CWD "++Path),
 123 server_verify_message(recv_response(Sock), 250),
 124 send_command(Sock, "TYPE I"),
 125 server_verify_message(recv_response(Sock), 200),
 126 send_command(Sock, "PASV"),
 127 {_, Msg} =recv_response(Sock),
 128 server_message(Msg, ""),
 129 {Addr, NewPort} =parse_pasv(Msg),
 130 
 131 DataPid =spawn(ftp_down, get_data, [Addr, NewPort, LocalPath ++File, self()]),
 132 
 133 send_command(Sock, "RETR "++File),
 134 % 150 Opening BINARY mode data connection for 150 File status okay; about to open data connection.
 135 % 125 Downloading in BINARY file125 Data connection already open; transfer starting.
 136 % 550 Failed to open file
 137 {Num, Text} =recv_response(Sock),
 138 V =(Num ==150) or(Num ==125),
 139 if
 140 V ->
 141 server_message("~s", [Text]),
 142 DataPid !start_transfer,
 143 server_verify_message(recv_response(Sock), 226),
 144 DataPid !transfer_complete,
 145 receive
 146 bye ->
 147 ok
 148 end;
 149 true->
 150 ifNum ==550->
 151 server_message("~w", Text);
 152 true->
 153 ok
 154 end
 155 end,
 156 
 157 gen_tcp:close(Sock).