如何实现下载网上的文件(100分)

用delphi如何编码实现互联网上的某一个文件？最好有断点续传的功能。

有源代码最好。

断点续传——转给你
unit Unit1;

interface

uses
{}filectrl,inifiles,{}Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ScktComp, ExtCtrls;

type
Tbuf_char=array[0..4095] of char;
Tbuf_byte=array[0..4095] of byte;

type
TForm1 = class(TForm)
ClientSocket1: TClientSocket;
Memo1: TMemo;
Panel1: TPanel;
Edit1: TEdit;
Button1: TButton;
Edit2: TEdit;
Button3: TButton;
Button4: TButton;
Label2: TLabel;
Label3: TLabel;
Label1: TLabel;
procedure ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket);
procedure Button1Click(Sender: TObject);
procedure ClientSocket1Connect(Sender: TObject;
Socket: TCustomWinSocket);
procedure Edit1Change(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure Edit2Change(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
filename1:string; //本地文件名
serfilename:string; //服务器端文件名
serhost1:string; //服务器地址
can_rec1:boolean; //是否可以接收
stop1:boolean; //是否停止

end;

var
Form1: TForm1;
pos1:longint; //上次下载到的位置


implementation


{$R *.dfm}

function app_path1:string;
begin
result:=extractfilepath(application.ExeName);
end;


//接收一行数据//socket,超时，结束符
function socket_rec_line1(socket1:TCustomWinSocket;timeout1:integer;crlf1:string=#13#10):string;
var
buf1:Tbuf_char;
r1:integer;
ts1:TStringStream; //保存所有的数据

FSocketStream: TWinSocketStream;

begin

ts1:=TStringStream.Create('');
FSocketStream:= TWinSocketStream.create(Socket1, timeout1);


//while true do//下面的一句更安全,不过对本程序好象没起作用
while (socket1.Connected=true) do
begin

//确定是否可以接收数据
//只能确定接收的超时，可见WaitForData的源码
if not FSocketStream.WaitForData(timeout1) then break; //continue;

//这一句是一定要有的，以免返回的数据不正确
zeromemory(@buf1,sizeof(buf1));
r1 := FsocketStream.Read(buf1, 1); //每次只读一个字符，以免读入了命令外的数据
//读不出数据时也要跳出，要不会死循环
if r1=0 then break; //test
//用FsocketStream.Read能设置超时
//r1:=socket1.ReceiveBuf(buf1,sizeof(buf1));
ts1.Write(buf1,r1);

//读到回车换行符了
if pos(crlf1,ts1.DataString)<>0 then
begin
break;
end;

end;

result:=ts1.DataString;

//没有读到回车换行符,就表示有超时错，这时返回空字符串
if pos(crlf1,result)=0 then
begin
result:='';
end;

ts1.Free;
FSocketStream.Free;

end;


function get_host1(in1:string):string;
begin
in1:=trim(in1);
if pos('http://',lowercase(in1))=1 then
begin
in1:=copy(in1,length('http://')+1,length(in1));
end;
if pos('/',in1)<>0 then
begin
in1:=copy(in1,0,pos('/',in1)-1);
end;
result:=in1;
end;

function get_file1(in1:string):string;
begin
in1:=trim(in1);
if pos('http://',lowercase(in1))=1 then
begin
in1:=copy(in1,length('http://')+1,length(in1));
end;
if pos('/',in1)<>0 then
begin
in1:=copy(in1,pos('/',in1)+1,length(in1));
end;
result:=in1;

end;

procedure TForm1.ClientSocket1Read(Sender: TObject;
Socket: TCustomWinSocket);
begin
memo1.Lines.Add(socket.ReceiveText);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
url1:string;
buf1:Tbuf_byte;
rec1:longint;
f1:file;

cmd1:string; //这一行的内容
reclen1,real_reclen1:longint; //服务器返回的长度;实际已经收到的长度
value1:string; //标志们的值
total_len1:longint; //数据总长

begin
try

//self.filename1:='c:/temp1.dat';
assignfile(f1,self.filename1);
can_rec1:=false;
self.stop1:=false;

if FileExists(self.filename1)=true then
begin
reset(f1,1);
pos1:=filesize(f1);
end
else
begin
rewrite(f1,1);
pos1:=0;
end;

seek(f1,pos1);


ClientSocket1.Active:=false;
ClientSocket1.Host:=get_host1(edit1.Text);
ClientSocket1.Port:=80;


url1:='';

self.serfilename:=get_file1(edit1.Text);
self.serhost1:=get_host1(edit1.Text);

//取得文件长度以确定什么时候结束接收[通过"head"请求得到]

ClientSocket1.Active:=false;
ClientSocket1.Active:=true;
url1:='';

url1:=url1+'HEAD /'+self.serfilename+' HTTP/1.1'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
url1:=url1+'Pragma: no-cache'+#13#10;
//新的
url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//下面这句必须要有
//url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Host: '+self.serhost1+#13#10;
url1:=url1+#13#10;

ClientSocket1.Socket.SendText(url1);

while ClientSocket1.Active=true do
begin

if self.stop1=true then break;

cmd1:=socket_rec_line1(ClientSocket1.Socket,60*1000);

//计算文件的长度

if pos(lowercase('Content-Length: '),lowercase(cmd1))=1 then
begin
value1:=copy(cmd1,length('Content-Length: ')+1,length(cmd1));
total_len1:=strtoint(trim(value1));
end;

//计算文件的长度_end;

if cmd1=#13#10 then break;
end;

//取得文件长度以确定什么时候结束接收_end;

//发送get请求，以得到实际的文件数据

clientsocket1.Active:=false;
clientsocket1.Active:=true;

url1:='';

//url1:=url1+'GET http://clq.51.net/textfile.zip HTTP/1.1'+#13#10;
//url1:=url1+'GET /textfile.zip HTTP/1.1'+#13#10;
url1:=url1+'GET /'+self.serfilename+' HTTP/1.1'+#13#10;
url1:=url1+'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*'+#13#10;
//应该可以不要url1:=url1+'Accept-Language: zh-cn'+#13#10;
//应该可以不要url1:=url1+'Accept-Encoding: gzip, deflate'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
//url1:=url1+'Pragma: no-cache'+#13#10;
//新的
//url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//接受数据的范围,可选
//url1:=url1+'RANGE: bytes=533200-'+#13#10;
url1:=url1+'RANGE: bytes='+inttostr(pos1)+'-'+#13#10;
//下面这句必须要有
//url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Host: '+self.serhost1+#13#10;
//应该可以不要
//url1:=url1+'Connection: Keep-Alive'+#13#10;
url1:=url1+#13#10;
ClientSocket1.Socket.SendText(url1);

while ClientSocket1.Active=true do
begin

if self.stop1=true then break;

cmd1:=socket_rec_line1(ClientSocket1.Socket,60*1000);

//是否可接收
if pos(lowercase('Content-Range:'),lowercase(cmd1))=1 then
begin
can_rec1:=true;
end;

//是否可接收_end;

//计算要接收的长度

if pos(lowercase('Content-Length: '),lowercase(cmd1))=1 then
begin
value1:=copy(cmd1,length('Content-Length: ')+1,length(cmd1));
reclen1:=strtoint(trim(value1));
end;

//计算要接收的长度_end;

//头信息收完了
if cmd1=#13#10 then break;
end;

real_reclen1:=0;
while ClientSocket1.Active=true do
begin


if self.stop1=true then break;

//不能接收则退出
if can_rec1=false then break;

//如果文件当前的长度大于服务器标识的长度,则是出错了，不要写入文件中
if filesize(f1)>=total_len1 then
begin
showmessage('文件已经下载完毕了！');
break;
end;

zeromemory(@buf1,sizeof(buf1));
rec1:=ClientSocket1.Socket.ReceiveBuf(buf1,sizeof(buf1));

//如果实际收到的长度大于服务器标识的长度,则是出错了，不要写入文件中
if real_reclen1>=reclen1 then
begin
showmessage('文件已经下载完毕了！');
break;

end;
//如果当前的长度大于服务器标识的长度,则是出错了，不要写入文件中
if pos1=reclen1 then
begin
showmessage('文件已经下载完毕了！');
break;

end;

blockwrite(f1,buf1,rec1);

real_reclen1:=real_reclen1+rec1;

Label1.Caption:=FormatFloat('#,##',real_reclen1)+'/'+FormatFloat('#,##',reclen1);
Label1.Caption:=Label1.Caption+'->'+inttostr(trunc((real_reclen1/reclen1)*100))+'%';
application.ProcessMessages;



end;

closefile(f1);
showmessage('ok');

//发送get请求，以得到实际的文件数据_end;

ClientSocket1.Active:=false;

except
closefile(f1);
showmessage('discon...');
end;


end;

procedure TForm1.ClientSocket1Connect(Sender: TObject;
Socket: TCustomWinSocket);
var
url1:string;
begin
{ url1:='';

url1:=url1+'GET http://clq.51.net/textfile.zip HTTP/1.1'+#13#10;
url1:=url1+'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*'+#13#10;
//应该可以不要url1:=url1+'Accept-Language: zh-cn'+#13#10;
//应该可以不要url1:=url1+'Accept-Encoding: gzip, deflate'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
url1:=url1+'Pragma: no-cache'+#13#10;
//新的
url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//接受数据的范围,可选
url1:=url1+'RANGE: bytes=533200-'+#13#10;
//下面这句必须要有
url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Connection: Keep-Alive'+#13#10;
url1:=url1+#13#10;
ClientSocket1.Socket.SendText(url1);

}
end;

procedure TForm1.Edit1Change(Sender: TObject);
var
ini1:tinifile;
begin
ini1:=tinifile.Create(app_path1+'sys1.ini');
ini1.WriteString('file1','host1',edit1.Text);

ini1.Free;

end;

procedure TForm1.FormCreate(Sender: TObject);
var
ini1:tinifile;
begin
ini1:=tinifile.Create(app_path1+'sys1.ini');
edit1.Text:=ini1.ReadString('file1','host1',edit1.Text);
self.filename1:=ini1.ReadString('file1','filename1','c:/temp1.dat');
edit2.Text:=self.filename1;
//pos1:=filesize(
ini1.Free;


end;

procedure TForm1.Edit2Change(Sender: TObject);
var
ini1:tinifile;
begin
ini1:=tinifile.Create(app_path1+'sys1.ini');
ini1.WriteString('file1','filename1',edit2.Text);

self.filename1:=edit2.Text;
ini1.Free;

end;

procedure TForm1.Button3Click(Sender: TObject);
var
url1:string;
buf1:Tbuf_byte;
rec1:longint;
f1:file;

cmd1:string; //这一行的内容
reclen1,real_reclen1:longint; //服务器返回的长度;实际已经收到的长度
value1:string; //标志们的值

begin
self.stop1:=false;

ClientSocket1.Active:=false;
ClientSocket1.Host:=get_host1(edit1.Text);
ClientSocket1.Port:=80;
ClientSocket1.Active:=true;

url1:='';

self.serfilename:=get_file1(edit1.Text);
self.serhost1:=get_host1(edit1.Text);
//url1:=url1+'GET http://clq.51.net/textfile.zip HTTP/1.1'+#13#10;
//url1:=url1+'GET /textfile.zip HTTP/1.1'+#13#10;
url1:=url1+'GET /'+self.serfilename+' HTTP/1.1'+#13#10;
//url1:=url1+'HEAD /'+self.serfilename+' HTTP/1.1'+#13#10;
url1:=url1+'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*'+#13#10;
//应该可以不要
//url1:=url1+'Accept-Language: zh-cn'+#13#10;
//应该可以不要
//url1:=url1+'Accept-Encoding: gzip, deflate'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
//url1:=url1+'Pragma: no-cache'+#13#10;
//新的
//url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//接受数据的范围,可选
//url1:=url1+'RANGE: bytes=533200-'+#13#10;
url1:=url1+'RANGE: bytes='+inttostr(533263)+'-533263'+#13#10;
//下面这句必须要有
//url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Host: '+self.serhost1+#13#10;
//应该可以不要
//url1:=url1+'Connection: Keep-Alive'+#13#10;
url1:=url1+#13#10;
ClientSocket1.Socket.SendText(url1);


//while ClientSocket1.Active=true do
begin
zeromemory(@buf1,sizeof(buf1));
rec1:=ClientSocket1.Socket.ReceiveBuf(buf1,sizeof(buf1));

real_reclen1:=real_reclen1+rec1;

memo1.Lines.Add(strpas(@buf1));

application.ProcessMessages;
//if self.stop1=true then break;
end;

ClientSocket1.Active:=false;

showmessage('ok');


end;

procedure TForm1.Button4Click(Sender: TObject);
begin
self.stop1:=true;
end;

end.

谢谢飞侠哥，分不会少了您的。
这段代码我见过，可是只能下载http的，而且对于地址重定向无能为力。
ftp的如何下载？
smtp？
这些协议到什么地方去找？
关注！

你看一下http协议就知道了

referer:应该是可以有判断得。很多下载网站都是这样得。

这么复杂我给你写一个简单的
用URLMON单元的URLDOWNLOADTOFILE函数

请问humanc2d4,你所说的"用URLMON单元的URLDOWNLOADTOFILE函数"指的是什么，如果你有这个单元，能发给我吗?先行谢过。

to humanc2d4,
URLMON单元?哪里有？